A generalized equivalent-particle theory for the the solitons governed by the nonlinear Schrodinger equatinon, with an operator- perturbation term included, is proposed, which can make understanding of the particle properties of solitons. As a parturbation method, it is able to deal with a wide kinds of problems, such as loss and gain in optical fiber, the effect of Raman induced scattering and higher order diapersions. The soliton interaction in optical fiber is analyzed by this method and the conclusions which are strictly in keeping with the results obtained by the inverse scattering technique and the variational perturbation theory are achieved. By using this method, the interaction of multi-soliton can be analytically analyized, and gives a visual picture of the physical process.