Introducing other regenerated tree species and forming mixed forest is fundamental solution of con- tinuous planting obstacle in artificial pure forest.In order to knowing the feasibility of mix-forestation of Larix kaempferi,Pinus tabulae formis,Catalpa fargesii and Quercus aliena var.acuteserrata in Qinling Mountains of China,situ incubations of humus soil mixture of different forests were carried out for 2 years to model the experiment of mix-forestation and the interspecific relationships of different trees were studied through analyzing the influences of soil mixture on the biochemical characteristics and litter decomposition. The results can be concluded as following:(1)In needle-leaved forests,microbiomass,enzyme activities of soil and annual litter decomposition rate were intensified after introducing broad-leaved tree species.The in- tensification increased with ratio of introduced broad-leaved trees and intensification of Cazalpa fargesii was greater than its of Quercus aliena.(2)In broad-leaved forests,although microbiomass,enzyme activities of soil and annual litter decomposition rate were also intensified after introducing a few needle-leaved species trees,the intensification decreased with ratio of introduced needle-leaved trees and intensification of Pinus tabulae formis was greater than its of Larix kaempferi.(3)In summary,interspecific relationship between the 4 typical tree species are harmonized in point of soil biochemistry and litter decomposition and it between Pinus tabulae formis and Catalpa fargesii is the best,its between Larix kaempferi and Catalpa fargesii, Pinus tabulaeformi and Quercus aliena are second,it between larix kaempferi and Quercus aliena is the worst.