Background With the severe situation of the increasingly population aging in China, the health problems of the middle-aged and older adults can not be ignored, attracting much attention on the health equity among the rural-dewlling middle-aged and older adults. The geographic remoteness of southern mountainous area in the Ningxia Hui Autonomous Region causes the health conditions of the middle-aged and older adults more unoptimistic. However, there are relatively few studies on the health equity among the middle-aged and older adults in this area. Objective To investigate the health equity of the middle-aged and older adults in the pilot counties of medical reform in the Ningxia Hui Autonomous Region (Haiyuan County and Yanchi County) and analyze the contribution degree of various influencing factors to health inequality, so as to provide a basis for improving the health of the middle-aged and older adults and relevant health policies. Methods From January to March in 2022, from the follow-up data of 2019 from the Family Health Inquiry Survey of Rural Residents, the middle-aged and older adults (age≥45 years old) from resident families (living in the corresponding counties for more than one year) were selected as subjects (n=5 908) . The analysis was conducted with the two-week prevalence rate, chronic disease prevalence rate, two-week bedridden rate and two-week leaving rate as dependent variables, with sex, age, marital status, level of education, occupation, type of drinking water and per capita family income as independent variables. The concentration index was used to analyze the health equity of the middle-aged and older adults, and the centralized index decomposition method was used to analyze the contribution of various influencing factors to health inequality. Results The concentration indexes of two-week prevalence rate, chronic disease prevalence rate, two-week bedridden rate and two-week leaving rate among the middle-aged and older adults in Haiyuan County were 0.030 0, 0.002 9, 0.011 4 and 0.032 7, respectively, while those of two-week prevalence rate, chronic disease prevalence rate, two-week bedridden rate and two-week leaving rate among the middle-aged and older adults in Yanchi County were 0.000 4, -0.000 1, 0.037 4 and 0.037 4, respectively. The concentration index decomposition analysis showed that gender, age, level of education, occupation, type of drinking water and per capita family income are the main causes for health inequality among the middle-aged and older adults, among which age and per capita family income contribute more to health inequality. The contribution ratio of age to the two-week prevalence rate, hronic disease prevalence rate, two-week bedridden rate and two-week leaving rate in Haiyuan County were -11.92%, -152.57%, -27.76% and 7.80%, respectively. The contribution ratio of age to the two-week prevalence rate, chronic disease prevalence rate, two-week bedridden rate and two-week leaving rate in Yanchi County were -334.79%, 1 117.94%, -45.45% and-25.44%, respectively. The contribution ratio of per capita family income to the two-week prevalence rate, chronic disease prevalence rate, two-week bedridden rate and two-week leaving rate among the middle-aged and older adults in Haiyuan County were 35.41%, -0.31%, 2.08% and 22.03%, respectively. The contribution ratio to the two-week prevalence rate, chronic disease prevalence rate, two-week bedridden rate and two-week leaving rate among the middle-aged and older adults in Yanchi County were 86.88%, -165.24%, 37.13% and 1.50%, respectively. Conclusion Overall, the health equity among the middle-aged and older adults in the pilot counties of the Ningxia Hui Autonomous Region is better but tilted towards those with higher incomes. Age contributes the most to health inequity among the middle-aged and older adults. The society should give higher priority to the middle-aged and older adults; Local primary health care institutions can increase the health awareness of the middle-aged and older adults by providing free health check-ups regularly and promoting health literacy to them. The health administration should adjust relevant health policies to better meet the health needs of the middle-aged and older adults and ultimately achieve health equity.