Despite the inarguable importance of arbuscular mycorrhizal fungi (AMF) in terrestrial ecosystems, we know little about how AMF communities shift in response to climate changes. In this study, we investigated the impacts of seven years of precipitation increment and nitrogen (N) addition on the taxonomic and phylogenetic diversity of AMF communities in a temperate steppe of northern China. Phylogenetic patterns were also used to elucidate the ecological processes structuring AMF communities. By 454-pyrosequencing, we detected a total of 71 AMF operational taxonomic units (OTUs), consisting mainly of Glomeraceae. In general, N addition reduced but precipitation increment increased AMF abundance including root colonization and fungal biomass. Nitrogen addition also decreased AMF alpha-diversity, including OTU richness, Chao 1 and Faith's phylogenetic diversity. Moreover, permutational multivariate analysis of variance showed that AMF community composition shifted in response to both N addition and precipitation increment. AMF communities were phylogenetically clustered across all experimental treatments, suggesting that environmental filtering was the primary driver of AMF community assembly. Taken together, these findings supported that both N and precipitation shaped the AMF communities, but not altered the ecological processes responsible for the assembly of AMF communities in the temperate steppe.