Abstract: Long period fiber gratings have the advantages of small size, corrosion resistance, anti-electromagnetic interference and high sensitivity, making them widely used in biomedical, power industry and aerospace. In this paper, a long period fiber grating sensor based on periodic microchannels is proposed. Firstly, a series of linear structures are etched in the cladding of a single-mode fiber by femtosecond laser micromachining. Then the laser-modified region is selectively eroded by selective chemical etching to obtain the periodic microchannel structure. Finally, the channels are filled with polydimethylsiloxane (PDMS) to improve the spectral quality. The temperature sensitivity is -55.19 pm/°C, the strain sensitivity is -3.19 pm/με, the maximum refractive index sensitivity is 540.28 nm/RIU and the bending sensitivity is 2.65 dB/m-1. And all of them show good linear response. The sensor has good application prospects in the field of precision measurement and sensing.