Abstract: Circuit models and mathematical expressions are built to analyse how much the circuit parameters of induction cavity affect the flattop of the induction pulse voltage. Two kinds of pulse-power system (PPS) are considered, one is based on the pulse forming lines (PFL) and pulse transmission lines, and the other is based on the capacitors and solid state switches. Much difference appears when the cavity works with different PPS. Using the comparison expressions including capacitance, inductance and resistance of the induction cavity and corresponding PPS, we can determine the circuit parameters of a pulse induction module exactly and easily.