The different PID control strategies of waste-gate were used under different transient conditions to establish the transient calculation model of turbocharged gasoline engine. The transient response under constant torque acceleration and deceleration conditions was simulated and compared with the transient response of original engine. The results show that the transient response is improved remarkably when the transient control target value takes the greater boost pressure at each fixed speed. In constant torque deceleration condition, transient response time is shorten when using the strategy that makes the waste-gate fully open in early stage until the speed reaches 1.25 times of the target speed, and then switches the control target to the boost pressure. At the same time, this way not only improves the transient response performance of the engine, but also prevents the turbocharger from surging and overspeeding under transient conditions.