The parametric gain of the ring and standing cavities was studied in this paper. By using the strong output of frequency doubled and stabilized Nd:YAP laser at 0．54μm as the pump source and the fundamental output at 1．08μm as the signal and idler modes, strong coupling of three modes in the ring or standing cavities is demonstrated. An optical wedge and a temperature controller are used to realize the three mode resonance simultaneously. Parametric gain as high as 110 is obtained. The relation between the gain and the pump power is also measured and the result fits to the theory on the whole.