A computational method for propagation velocity of methane explosion flame was developed based on correlation coefficients of images. Images of propagating flame were captured by a high-speed camera at a very high frequency. In order to calculate the displacement between two adjacent images of flame, the correlation coefficients were utilized. By trimming the two adjacent images and computing the correlation coefficients, the actual displacement of flame was obtained, and the average velocity of flame between two images was subsequently obtained. The flame velocities at different concentrations of methane were calculated during the whole process of explosion. The results showed that explosion flame undergoes a process of acceleration, deceleration, reverse acceleration, and reverse deceleration. By comparing with the measured velocity, the relative error is found to be very tiny. The method can be used to calculate not only the velocity of flame front but also the velocity of the flame wherever it is in the pipe.