An eye-safe laser source at 1.57 μm is demonstrated by using a non-critically phase-matched (θ=90°, φ=0°) ring cavity optical parametric oscillator pumped by an electro-optic Q-switched Nd:YAG laser. Theoretical and experimental results show that reducing the cavity length and injection of seed laser can effectively reduce the threshold, and increase the output energy. When the Nd:YAG laser energy is 88 mJ and the injected signal power changes from 0 to 6 mW, the output energy is enhanced from 8.8 to 14 mJ. When the pump energy is 167.7 mJ and the injected signal power is 6 mW, the maximum output energy of 46 mJ is obtained, corresponding to the peak power of 7.44 MW.