A flexible force sensor based on the spheroidal Fabry-Perot micro-cavity is proposed. Through theoretical analysis and simulation, we find out that the relationship between cavity length and force sensitivity is negatively correlated. Then two Intrinsic Fabry-Perot Interferometers with cavity lengths of 59.5 um and 65.3 um are fabricated by chemical etching. The force and temperature experiments are implemented, and the results show that the force sensor has good linearity and stability. The force sensitivity and temperature sensitivity of the flexible Fabry-Perot force sensors are 106 pm/N, 4.3 pm/℃ and 104 pm/N, 4.2 pm/℃ respectively. In addition, the flexible Fabry-Perot force sensor has advantages of lightweight, high flexibility, compact structure and low force-temperature cross sensitivity, which is expected to be used in the robot finger force sensing, the pulse vibration detecting and the surgical instruments clamping force monitoring in the future.