In order to measure the strain with high sensitivity and high resolution， an OCMI strain measuring system based on dispersion enhancement was established. Firstly， the transfer function of OCMI strain sensing system was derived based on double-sideband modulation theory， and the mapping relationship between FBG optical wavelength drift and microwave frequency was obtained. Then， a strain sensing system was built， and the sensitivity of the system under different dispersion combinations was compared by monitoring high frequency frequencies. It was shown that reverse access to LCFBG could effectively enhance the sensitivity， and the greater the dispersion of LCFBG， the greater the sensitivity of the system. The experimental results show that the sensitivity of the dispersion-enhanced strain sensing system can reach 43.75 kHz/μɛ， which is 42 times that of the system without LCFBG. The scheme proposed in this paper has high stability and resolution， which provides a reference method for the measurement of weak physical quantities.