This paper studied the bifurcation and chaos phenomenon in a multi-parallel-connected current-mode controlled boost DC-DC converter system with the use of nonlinear mapping bifurcation theory of two dimensions,and the changing rules of the bifurcation charts with the increase of the control parallels and control parameters were concluded.The method of discrete mapping modeling was utilized to construct the difference equations of the system operating in continuous conduction mode (CCM).Analyses and computer emulations were made.