A experimental study of widely tunable periodically poled MgOLiNbO3 (PPMgLN) optical parametric oscillator (OPO) is presented. The laser diode (LD) end-pumped acousto-optically (A-O) Q-switched NdYVO4 laser was used as the pump source of OPO. The OPO resonator consisted of a two CaF2 concave mirror linear cavity. By varying temperature (30~80 ℃) and poling periods (29.0~31.5 μm) of PPMgLN crystal, the signal wavelength was tunable in the range of 1450~1700 nm as well as the idle wavelength was tuned from 2849.0~3989.4 nm. The measured full width at half maximum ( FWHM) of the output signal and idler ware were about 0.58 and 4 nm or less, respectively. The results indicate that the experimental data agrees well with the calculated tuning curve.