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[Objective] To explore the effects of weather factors such as temperature, precipitation and sunshine hours on the incidence of powdery mildew in winter grapes harvested twice a year under rain-shielding cultivation mode, and provide theoretical basis for the prevention and control of powdery mildew in winter grapes harvested twice a year. [Methods] Before the harvest of winter grapes in 2017 and 2018, the field natural identification method was used to investigate the incidence of powdery mildew in 14 grape varieties/plants under the sheltered cultivation mode, combining 2017 and 2018 September 1 The meteorological monitoring data from December 31 to December 31 is used to analyze the correlation between meteorological factors, the incidence of grape powdery mildew and the disease index. [Results] During the harvest of winter grapes in 2017, the incidence of powdery mildew in 11 grape varieties/lines was lower than in 2018, and the disease index of powdery mildew in 9 grape varieties/lines was lower than in 2018. The precipitation and the number of rainy days from September 1 to December 31, 2017 were greater than those of the same period in 2018; the number of days in the suitable temperature range for powdery mildew (20.0-27.0°C) in 2017 was less than in 2018; the total accumulated temperature in 2017 was slightly Higher than 2018; 2017 had more sunshine hours than 2018; the two-year average daily relative humidity in 2017 and 2018 was suitable for powdery mildew fungus conidia germination. [Conclusion] The main reasons for the occurrence of powdery mildew in grapes in the winter of 2018 are the main reasons why the occurrence of powdery mildew in grapes in the winter of 2018 is more serious than that in 2017. [ABSTRACT FROM AUTHOR]