Research conclusions :(1) The stress diffusion angle and lateral friction have significant effection on the calculation results of additional stress. When the value of stress diffusion angle or lateral friction changes， the substratum’s additional stress may focus or disperse. (2) The compression modulus ratio of reinforcement area to substratum of composite ground has also significant influence on the additional stress in substratum， but the additional stress only disperses generally when the value of this ratio changes. ( 3 ) The computing results of stress diffusion method，equivalent entity method and equivalent layer method are influenced greatly by their main computing parameters， Boussinesq method is more applicable to compute the substratum ^s additional stress. (4) The research conclusions have good references value for engineers to choose the calculation method for the substratum s additional stress.