Abstract: Some theoretical models of multi-species interaction have been constructed by some authors. But,it is difficult in experiments to determine interaction coefficients when the populations living together number more than 4 specks. In this paper,a rotation composite design of quadratic regression is suggested as a method to construct a mathematical model for describing the dynamics of populations interacting together. This mathematical model may be used to forecast the numerical changes in time interval,and may be helpful to input information on control effects in any population system with some species interacting together.