Aimed to explore the effects of different vegetations and of the years of vegetation restoration on soil microbial biomass carbon and nitrogen, a comparative study was conducted, with the 5 year old Robinia pseudoacacia, Hippophae reamnoide and Prunus armeniaca plantations and the 5, 15 and 25 years old R. pseudoacacia plantation in the Yangjuangou catchment of Yanan City of Shaanxi Province, a typical hilly area of the Loess Plateau, as test objects. The results showed that among the three 5-year old plantations, H. reamnoides plantation had the highest soil organic carbon (SOC) and total nitrogen (TN) contents, while R. pseudoacacia plantation had the highest soil microbial biomass carbon (MBC) (99.56 mg x kg(-1)) and nitrogen (MBN) (28.81 mg x kg(-1)). The MBC was in the order of R. pseudoacacia > H. reamnoides > P. armeniaca, and that of MBN was of R. pseudoacacia > P. armeniaca > H. reamnoides. The MBC/SOC was in the order of R. pseudoacacia > H. reamnoides > P. armeniaca, and that of MBN/TN was of R. pseudoacacia > P. armeniaca > H. reamnoides, with the differences being significant (P < 0.05). With the increasing years of vegetation restoration, the soil pH in R. pseudoacacia plantation decreased, while the SOC, TN, electricity conductance (EC), MBC, and MBN all had an increasing trend, which illustrated that in the hilly area of Loess Plateau, planting R. pseudoacacia was more beneficial to the increase of soil MBC and MBN, and, with the increasing years of this planting, soil MBC, MBN, SOC and TN tended to be increasing.