Resonance wavelength of long period fiber grating basically has a linear relation with the temperature changes, and the volatility of the wavelength corresponding to the loss peak can be represented by the standard deviation of the linear fitting. A new method for temperature sensing performance evaluation of long period fiber grating (LPFG) is proposed. The method is to use the ratio of the temperature sensitivity to the fitting standard deviation, P, to measure the sensing properties of LPFG. Lot of experimental results show that temperature sensitivity has a good consistence with the P value. The greater the P value is, the better the temperature sensing property of LPFG is, and the smaller the P value is, the poor the property is.