Abstract: The phase-matching mode of KTP-OPO was theoretically analyzed and calculated, and the angle-tuning curve of KTP-OPO was given. A 1.57 m eye-safe laser based on optical parametric oscillator was experimentally studied, which adopted KTP nonlinear optical crystal. Using a xeno-flash-lamp-pumped 1.064 m Nd∶YAG laser in intracavity KTP-OPO，under the repetition rate of 5 Hz, a laser output with the energy of 32 mJ and the pulse width of 7.22 ns was obtained. The optical-to-optical conversion efficiency was 41%, which makes long range laser range finding possible.