As optical solitons propagate along the fiber, stable bound state solitons can be formed due to complex nonlinear interactions, and phase variation of bound state solitons reveals abundant dynamics in the nonlinear system. Based on the Ginzburg-Landau equation governing the evolution of solitons along the fiber, the dynamics of soliton phase variation induced by the system parameters was numerically studied. It was found that there exist different bound state solitons, and initial conditions finally converge to bound state solitons with different phase difference. The results also indicate that the change of pump strength influences the pulse separation of solution as well as phase difference of bound state, which is of importance for in-depth understanding of the underlying nonlinear interaction mechanism.