An analytical transient turn-off current model for a type of the conductivity modulation power MOSFET transistors (CMT) with the extracted structure of the excess carrier is developed in the paper. With the non-quasistatic state (NQS) approximation for the excess carrier in the wide base of a low gain pnp transistor included in the CMT the three state equations of the charge, the voltage and the current are solved for the transient turn-off current analysis and ambipolar transport theory in high-level injection is used to evaluate the steady state current. Accounting for the perturbing effect of the carrier concentration redistribution under the condition of base width modulation and the coupling effect between the electron and hole current, phe normalized transient current and turn-off time of the device with the extracted structure are obtained and compared with the experimental results.