Abstract: Spatial differentiation of allozymes among 21 natural populations of Castanea mollissima was investigated using F-statistics and spatial autocorrelation analysis.Most alleles were found to be random spatial patterns and lack of spatial structure,while a few were non-random patterns of cline or double cline with apparent spatial structure.The spatial patterns of genetic differentiation in C.mollissima populations appeared to be a combining result of long-distance gene flow,climate factors,human activities,and local effects of geographic isolation.The spatial structure was consistent with the hypothesis that Yangtze River valley should be the relict centre,which gave rise to northern and southern populations after the last glacier.The monsoon and human activities were probably the factors in shaping the spatial genetic structure of C.mollissima populations,while the ecological gradient selection created the cline distribution from North to South.