Long-term management of planted pure forest will lead to continuous planting obstacle and influence the sustainable development of forest. The best solution is to form mixed forest through introducing other regenerated tree species. In order to direct the option of mixed tree species and ratios on upper reach of Minjiang river, situ incubations of soil mixture (soil of coniferous forest with deciduous) of typical forests of Cercidiphyllum japonicum, Betula utilis, Pinus yunnansinsis and Picea asperata were carried out and the interspecific relationships of different tree species were studied through analyzing the influences of soil mixing of different forests on the biochemical characteristics and litter decomposition, according to the comparison of practical biochemical indexes of mixed soil with its theoretical predicted value (weighted average of soil mixture). The results can be concluded as following: (1) In forestlands of C .japonicum, P. yunnansinsis and P. asperata, soil enzyme activities of urease, sucrase and catalase were intensified after mixing their soil with others. Whereas, in forestland of B. utilis, all the three soil enzyme activities were reduced after mixing with soil of P. yunnansinsis, but enzyme activities of urease and catalase were intensified and enzyme activity of sucrase was reduced after mixing with soil of P. asperata. (2) In forestlands of C .japonicum and P. yunnansinsis, the contents of organic-C and total N in soil were increased after mixing their soil with others. Whereas, in forestland of B .utilis and P. asperata, the contents of N in soil were increased while contents of organic-C were decreased after mixing their soil with others. (3) In all forestlands of the 4 tree species, the acidities or alkalinity of soil were neutralized after mixing their soil with others. This means that soil of deciduous forest develops forward to acidity while soil of coniferous forest develops forward to alkalinity. (4) In all forestlands of the 4 tree species, the rapids of litter decomposition were advanced after mixing their soil with others. (5) According to the comprehensive effects of soil mixing, LM 0.15-0.50 and LY 0.15-0.35 in forestland of C. japonicum, HM 0.15 and HY 0.15-0.50 in forestland of B. utilis, ML 0.15-0.50 and MH 0.35-050 in forestland of P . yunnansinsis, YL 0.35-0.50and YH 0.35 in forestland of P. asperata are better choice for soil mixing relatively, which can be taken as reference in decision of regenerated tree species and mixing ratio of forest in practice.