Abstract: Seasonal changes and distributions of the soil microbial biomass nitrogen(SMBN) in different layers of soil in the main areas of evergreen broad-leave forest in Mt. Wuyi were studied during 2010 and 2011. The correlations among SMBN, total nitrogen(TN), organic carbon(SOC) and microbial biomass carbon(SMBC) in the soil were examined. The environmental factors affecting the results were identified. It was found that(a) SMBNs were higher in summer and autumn than in spring and winter;(b) the seasonal changes of TN was not significant;(c) SMBN of G1(0-10 cm) soil were higher than G2(10-20 cm) and G3(20-30cm);(d) SMBN was not significantly different between G2 and G3;(e) SMBN decreased from top to lower layers;and(f) SMBN, STN, SOC and SMBC in 0-30 cm soil showed a significant correlation(P<0.01). The results suggested that SMBN was significantly affected by the organic matters presented in the soil.