Cr4+:YAG is a new saturable absorber for passive Q-switching. As a passive Q-switcher, it has several excellent properties, such as low saturation fluence, high damage threshold, good thermal conductivity, no degradation and so on. By using a laser-diode as pumping source and Cr4+ :YAG as passive Q switcher, the passive Q-switching run in Nd: Sr5(VO4)3F laser at 1. 065 μm is realized. The average output power, the single pulse energy, the pulse width and the repetition rate for different small-signal transmission of Cr4+:YAG and different pumping power were measured. Meanwhile, the coupling rate equations for Cr4+:YAG as passive Q-switcher were given and the experimental results agreed with the numerical solution of equations.