The discreteness of device parameters exists in the analog signal processing using conventional phase measurement methods, and the error caused by threshold voltage of comparator is difficult to estimate and eliminate. Due to this shortcoming, a method based on TMS320F28335 eCAP module for measuring the phase difference is presented. Firstly, the AC signal is amplified and filtered to eliminate the error introduced by electromagnetic interference, and then the digital signal through the Schmitt Trigger designed by CPLD is converted to wave signal with the same frequency of the signal, by capturing the edge-triggered, enters the capture interruption subroutine to calculate the number of the sampling points of one period, finally the phase difference is calculated according to correlation method. Hardware circuit and software flow chart are given. The experimental results verify the method has higher reliability and precision than conventional methods.