A rate-equation-based model is established to describe the behavior of an intracavity optical parametric oscillator (OPO) pumped in an actively -switched Raman laser system. The intracavity photon densities and the initial population inversion density are assumed to be Gaussian distribution. These coupled rate equations are solved numerically. In the experiment, a laser diode end-pumped acousto-optically -switched KTP-OPO pumped by a Nd:YAG/ Raman laser is demonstrated. The output characteristics are studied carefully. And the experimental results about the average output power agree with the numerical solutions.