The temperature-tuning characteristic of periodically poled crystal, taking MgOsPPLT as an example, in the optical parameter process in the near infrared range with 532 nm pumping laser is studied by considering Sellmeier equation for the change of crystal refractive index with wavelength and temperature, the thermal expansion of poled period with temperature, and the energy conservation condition during frequency conversion process. By increasing the poled period, the non-temperature-sensitive characteristic at the mid-infrared range with 1064 nm pumping laser is also obtained. Just by adjusting or ignoring the poled period term, and replacing the crystal dispersion equation, the method can be easily extended to other quasi-phase matched or phase-matched nonlinear crystals.