A new type of the optical fiber fluid pressure sensor was designed and studied. Firstly, the sensor system was designed based on the principle of intensity compensation, and the compensation model of the sensor system was established. Then, the optical 〖JP2〗fiber fluid pressure sensor probe based on piston structure was presented, and the mathematical model of sensor was established. Finally,〖JP〗 on the basis of theoretical analysis, the sensor was studied, and the p-M curves under different structural parameters NA、l、d values were obtained.The experimental results show that there is a linear relationship between the output value of the sensor and the pressure p, and the sensor has good sensitivity. The results show that the sensor can meet the requirements of different occasions.