In view of the sensor problems, such as insufficient function, large size, low measurement accuracy, existing in the conventional detection methods for the hydraulic system, a compound sensor based on fiber Bragg grating was designed. On the basis of the integration of target-type flow sensor, the sensor combines with fiber Bragg grating temperature and pressure sensor simultaneously, so the flow, pressure and temperature of hydraulic system can be measured simultaneausly. Based on theoretical analysis of each parameter sensing model, the sensor structure was designed, and the sensor was produced in practice. The equipments such as hydraulic pressure colligation test system were used for the sensor performance testing and calibration. The results show that, the flow measurement sensitivity of the sensor is 0.049 L/s, the pressure sensor measurement sensitivity is 28.4 pm/Mpa, the temperature sensor measurement sensitivity is 14.9 pm/℃, and the sensor design reasonableness is verified. Meanwhile, the temperature measuring function of the sensor can be used as a reference fiber Bragg grating, when the fiber Bragg grating flow and pressure sensor are used in measurement, which can overcome the crossed sensitivity with temperature, and improve the sensor adaptability.