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【】The phase difference measurement takes an important role in fault diagnosis, dynamic characteristic analysis of linear system and some relative parameter measurements in electrical engineering field. In this paper, according to the principle, the phase difference for same cycle frequency signals is equal to the initial phase, a phase difference measurement is designed by calculating the initial phase of same cycle frequency signals, and combined with DFT non-integer correction algorithm. The system adopts a new generation of 32-bit ARM microprocessor based on cortex-M3 to design a complete system architecture for controlling and data processing. Besides, by using the engineering library of TI Company and DSP arithmetic library, the quasi-synchronous DFT non-integer correction algorithm can be realized, and based on Newton"s iterative algorithm and the relationship between phase difference and initial phase, the real phase difference can be calculated. After some tests, the results show that the system has a high accuracy of phase difference, and the minimum measurement precision can reach only 0.1°. At the same time, the wide frequency range is also suitable for phase difference measurement, which is accurate, stable and reliable in application.