Abstract: A compact, intra-cavity widely tunable continuous-wave singly resonant optical parametric oscillator (SR-OPO) was reported based on a MgO-doped periodically poled lithium niobate (MgO:PPLN). A diode-pumped Nd:YVO4 laser at 1 064 nm was employed as the pump source of this SR-OPO with a compact linear cavity. The MgO:PPLN crystal used contained seven different periodically poled gratings from 28.5 to 31.5 m with a step of 0.5 m between the neighbor periods. The output wavelengthes at the different grating periods of MgO:PPLN crystal was measured, which was well matched with the theoretical value. The widely tunable SR-OPO output signal wavelength range from 1.43 to 1.67 m and idler wavelength range from 2.93 to 4.16 m were achieved. The output power as the function of grating periods and pump power was investigated. Under an incident pump power of 14.5 W, a maximum signal output power of 2.94 W at 1 595 mm and an idler output power of 1.45 W at 3 190 nm were obtained with the temperature controlled at 35℃ and the period set at 31 m. The diode to OPO total output conversion efficiency reached 28.5%.