Phylogenetic diversity (PD), a measure of community diversity in terms of phylogenetic relatedness and evolutionary history, is widely used to explore patterns of plant diversity. It is frequently reported that the PD was significantly affected by some factors, such as paleoclimate and present climate. However, the previous results were inconsistent and the influence of soil nutrients on PD was overlooked. Based on PD surveyed from 310 sites in 8 different areas (Mt.Altai, Mt.western Junggar, Junggar desert, Mt.North Tianshan, Ily Valley, Mt.South Tianshan, Tarim basin, and Mt.Kunlun) in Xinjiang grassland, we explored effects of paleoclimate, present climate, soil nutrients, soil and grassland types on PD. Our results showed that: (1) Sites was firstly important factor regulating PD variation, followed by grassland and soil types, these three factors together explained 46.07%-78.80% of total variation in PD. Tarim basin, lowland meadow and frigid desert soil had the highest PD in terms of regions, grassland and soil types, while Junggar desert, temperate desert, and aeolian sandy soil had the lowest PD. (2) The variation of PD was also affected by precipitation anomaly since the Last Glacial Maximum (MAPano), mean annual temperature (MAT), precipitation seasonality (PS), and ratio of soil organic carbon to total nitrogen (C ∶ N). The PD in Xinjiang grassland, Mt.western Junggar, Ily Valley, and Mt.Kunlun all exhibited a unimodal pattern (increased firstly and then decreased) with increasing MAPano. With increasing MAT, the PD in Xinjiang grassland decreased firstly and then increased, but linearly decreased in Junggar desert and exhibited a unimodal pattern in Ily Valley and Mt.Kunlun. Along PS gradient, the PD in Mt.Altai and Ily Valley exhibited a unimodal pattern but linearly decreased in Mt.Kunlun. Only PD in northern Xinjiang was significantly affected by soil C ∶ N and decreased firstly and then increased. (3) Compared with previous studies which focused on species richness, we found that PD responded contrastly or differently along environmental gradient due to variation of relatedness among species in community. Our study highlighted importance of PD in understanding relationship between diversity and environmental gradient and diversity conservation in future.