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 μm with a step of 0.5 μm 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 μm and idler wavelength range from 2.93 to 4.16 μm 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 μm. The diode to OPO total output conversion efficiency reached 28.5%.