The solutions of rate equations in a high power all solid-state Q-switched intracavity frequency doubled laser by taking the phase mismatch into account are presented. By taking acousto-optical Q-switched intracavity frequency doubled Nd:YAG laser for example, rate equations under phase mismatch were described and solved numerically. The influence of phase mismatch and pump power on output power, pulse width in Q-switched intracavity frequency doubled laser were analyzed theoretically.