Temperature tuning and domain period tuning optical parametric oscillator based on periodically poled MgO doped lithium niobate (PPMgLN) in singly-resonant was studied experimentally. The output spectrum of optical parametric oscillator was discussed. A laser diode (LD) end-pumped acousto-optically Q-switched Nd:YVO4 laser was used as the pump source. The double-concave cavity structure was employed as PPMgLN-optical parametric oscillator (OPO) resonance cavity. Under Q-switch repetition rate of 10 kHz and temperature of 25.4 ℃, the threshold pump power of 110 mW is gained. The signal output power of 84 mW is obtained with a pump power of 325 mW and optical-optical conversion efficiency is 25.8%. It generates signal wave-lengths tunable in the range of 1449.6～1635 nm by temperature tuning and domain period tuning of PPMgLN. The spectrum from frequency mixing between the pump and signal is obtained at 25.4 ℃. The experimental results show that the full-width at half-maximum (FWHM) of output spectrum is less than 0.5 nm.