An algorithm for real-time demodulation of random turbulence phase difference is proposed according to the principle and signal expression of fiber optic turbulence measurement system. Fixed, waveform and random turbulence phase difference are all simulated and demodulated to demonstrate the applicability of the algorithm. Result shows that absolute error between demodulated and simulated phase difference is less than 10-3, which satisfies the demand of turbulence measurement. The research provides an important theoretical method to detect the dynamic phase difference of optical turbulence.