A photonic crystal fiber sensing system based on optical-borne microwave interference is built to solve the problem that the current photonic crystal fiber sensor is sensitive to inter-mode interference and difficult to package. The system interference occurs between the microwave envelopes of the optical carriers, the light does not interfere, and the polarization fading, dispersion, and inter-mode interference of the optical waves have a little effect on the signal quality. Therefore, the system does not require special processing for the photonic crystal fiber, with low requirements of the processing accuracy. Strain and high temperature sensing experiments are carried out on the system. The strain test results show that the visibility of interference fringe in microwave domain can reach 20 dB, the strain measurement sensitivity at 8 GHz is 6.3 kHz/με, and the resolution of the microstrain measurement is 1.59 με. The temperature experimental results show that temperature measurement sensitivity of system is 76.04 kHz/℃ from room temperature to 800 ℃, and the theoretical temperature measurement resolution is 0.13 ℃. Temperature experiments using multiple sets of length probes prove that the system has good temperature sensitivity and stability.