The Yb3+-doped fiber mode-locked laser using the polarization sensitive ISO and polarization controller(PC) is reported.In the normal dispersion,the fiber laser can oscillate the multipulse state by adjusting the position of the PC.If the polarizatioin state is constant,the output of Yb3+-doped fiber mode-locked laser changes from single pulse to multipulse with the increasing of the pump power.The fiber laser can achieve different multipulse output by adjusting the PC1 and PC2 carefully.The generation of the multipulse is induced by over-driving the fast artificial saturable absorber.