Using laser\"diode (LD) as pumping source, a passively Q\"switched Nd:GdVO4 laser at 1.06μm with Cr4+:YAG saturable absorber has been realized. By changing the distribution of the pump beam in the gain medium and the positions of the Cr4 + :YAG crystal in the cavity, the control of the pulse widths is realized easily. According to the distribution of beam radius along the cavity axis calculated through the well\"known ABCD matrix theory, the coupled rate equations of a LD\"pumped passively Q\" switched Nd:GdVO4 laser with Cr4+:YAG saturable absorber are given, in which the thermal effect of the gain medium and the Gaussian distribution of the pump beam and the oscillating laser intensity have been considered. The relations between the pulse width and the pump beam radius in the gain medium as well as the laser beam radius in the saturabe absorber are obtained from the numerical solutions of rate equations, and the theoretical calculations agree with the experimental results.