Temperature,strain and bending characteristics of a long period fiber grating(LPFG) written in a grapefruit-type photonic crystal fiber(PCF) are investigated experimentally.By using high-frequency CO2 laser,the LPFG written on PCF(PCF-LPFG) is achieved.The temperature sensitivity and strain sensitivity of PCF-LPFG resonant wavelength are 0.002 nm/℃ and 0.0018 nm/με,respectively.The PCF-LPFG resonant peak is insensitive to temperature or strain.The bending characteristics are directly related to curvature and bending direction.A direction with high sensitivity is chosen for further study.In a certain range of curvature,the bending sensitivity at PCF-LPFG resonant wavelength is-5.45 nm/m-1 and that at the resonant peak is 3.32 dB/m-1.Based on the special characteristics of PCF-LPFG,the paper provides new methods for fabricating temperature-insensitive strain and bending sensors.