High repetition frequency and low threshold laser with wavelength of 2 μm is reported using periodically poled MgO-doped lithium niobate (PPMgLN) with doped concentration of 5%. A 2 μm laser is obtained with PPMgLN pumped by a 1.064 μm laser and the corresponding relation between polarization period and the temperature is calculated. In experiments, the comparison of the efficiencies of two different polarization periods (32.2 μm and 32 μm) is carried on. We focus on the polarization period that has higher efficiency (32 μm) and conduct the experimental analysis of the oscillation threshold. Under the condition of the conversion efficiency is not less than 40%, the laser output with oscillation threshold of 0.046 MW/cm2 at near degenerate point(signal wavelength of 2.05 μm, idler wavelength of 2.236 μm) is achieved.