There is fragmented land and fragile ecological environment in the loess hilly and gully region. With the rapid population growth and socio- economic development in recent years, the degree of fragmentation has been further aggravated. Therefore, based on the interpretation data of remote sensing images in 1990, 2000 and 2015, this paper uses Fragstats 4.2 to obtain the best analysis scale combined with the standard method and moving window method. On this basis, the spatial differentiation characteristics of each landscape index are explored; The spatial and temporal evolution process of watershed landscape fragmentation is revealed; The spatial autoregressive model is used to analyze the impact factors contributing to landscape fragmentation. The results show that with the change of grain size and extent, some landscape indices show a regularity to certain degree. The 90 m grid size and 900 m square window size are the best analysis scales in the Fenhe River Basin; patch density, contagion, effective grid size, and Shannon's diversity index have a spatial agglomeration effect in the three periods, and the spatial agglomeration type distribution has strong similarity. From 1990 to 2015, the spatial pattern of landscape fragmentation in the study area has obviously changed; the slope, elevation and distance from the construction land are the main factors affecting landscape fragmentation of river basin during the three periods. The research results can provide reference for landscape fragmentation analysis in Northwest China, and provide basis for future regional landscape pattern optimization and effective land management. [ABSTRACT FROM AUTHOR]