Abstract: This study was aimed to discover the effects of different types of plantations on soil microbial community structure and functional diversity in hilly loess region. The study area is located in Jixian County, Shanxi Province of northern China. Two typical plantations (Robinia pseudoacacia and Pinus tabuliformis) were chosen and a grassland was set as control. Soil samples in the vertical layers (0-20 cm) were collected in August 2014, and soil microbial community structure was analyzed by phospholipid fatty acid (PLFA) analytical method. Results showed that the PLFA amounts of soil bacteria, fungi, actinomyces and Gram negative bacteria and Gram positive bacteria under the Robinia pseudoacacia plantation were all the highest in the three kinds of sample plots. Biomass of bacteria in three plots was significantly different, while that of fungi was roughly the same in the two plantations and significantly different with the grassland. Plantation improved the proportion of fungi. The phospholipid fatty acid structure of the two typical plantations was significantly different with the grassland. The correlation analysis showed that the amounts of the PLFAs were closely correlated to the soil fertility factors. Microbial community structure was correlated to plants: functional diversity was higher under the Robinia pseudoacacia plantation, followed by that under Pinus tabuliformis plantation, and grassland was the least. Therefore, for the microbial community, the two typical plantations can improve the microbial community structure and the soil quality as well, and Robinia pseudoacacia plantation was better.