Gain-switching and Q-switching are usual methods to obtain pulsed laser operation. For 1.3 μm wave band pulsed laser which is widely used in nonlinear optics, detection device used for optical communication second window and fiber sensor etc, gain-switching method is put forward to obtain the pulsed operation. Firstly, rate equation for the gain-switching is used to analyze the operation of laser. And the numerical simulation shows influence of the cavity length to pulse parameters. Secondly, the driver of LD is modulated to pump Nd:YVO4 laser working in the state of gain-switching. By decreasing the pulse width of the pumping current, the first pulse of relaxation is picked up. The 1.342 μm pulse with average power of 80 mW, pulse width of 200 ns, frequency of 200 kHz, peak power of 2 W and pulse energy of 0.4 μJ is obtained at last.