The vibration sensing technology based on optical frequency domain reflectometry (OFDR) has attracted a lot of research due to its superior electromagnetic interference resistance, good corrosion resistance, convenient installation and accurate positioning capability. Phase demodulation algorithm is the key technology of vibration sensing based on OFDR. There are many phase demodulation algorithms applied to OFDR vibration sensing, but they are more or less affected by modulation depth or light intensity. In order to reduce the impact of these two factors on the demodulation results at the same time, this paper proposes an improved phase generation carrier algorithm, which eliminates the nonlinear terms of the light intensity term and modulation depth term in the demodulation signal through mathematical calculation. Compared with the traditional algorithm from both theoretical and simulation aspects, the performance of the improved algorithm is verified, which can reduce the impact of these two factors on the demodulation results at the same time. The work of this paper can be used to improve the stability of the vibration sensing system.