A field plot sampling method was employed to investigate communities of natural forests in Zhouzhi Laoxiancheng Natural Reserve of Shaanxi.Parameters of niche breadth (B),niche similarity (L) and niche overlap (C) were calculated to analyze community characteristics.The results showed that:(1)243 species were recorded and they belong to 159 genera and 64 families.The plots were classified into 3 vegetation types and 9 formations.(2)Niche breadths of Pinus armandii and Quercus aliena var.acutiserrata were larger than other species in main tree populations,with Levins (B_i) and Hurlbert’s (B_a) values being 0.654 and 0.699,and 0.534 and 0.460 respectively;Smaller niche breadths were found in Quercus serrata var.brevipetiolata and Ulmus bergmanniana species,with B_i and B_a values being 0.064 and 0.023,and 0.049 and 0.016 respectively.(3)The species pairs which have higher niche similarity and niche overlap were Betula platyphylla and Populus purdomii,Populus davidiana and Betula utilis,with L_ij and L_ji values being 0.108 and 0.114,and 0.089 and 0.128,C_ij values being 0.939 and 0.744,respectively.The lower niche similarity and niche overlap among dominant species means less fierce interspecies competition and low spatial heterogeneity at current stage in the community succession.