Abstract: During the pulse compression process, dynamic parameters of magntic core experience two phase of unsaturated and saturated, and which correspond to a half hysteresis cycle. The diagnosis of the winding current and the change rate of magntic flux on the magnetic core provides necessary value for determining the hysteresis cycle, saturated magnetic flux intensity and retentiveness of magntic core. Principle of this diagnosis and method of dynamic parameters on magnetic core are discussed. The schematic circuit and optimizing method of circuit elements for diagnosis equipment are also given as well as the experimental results.