Abstract: Study of ignition transient characteristic of impulsive microthruster was conducted. The internal flow field of microthruster was simulated numerically by solving a 2-D symmetrical N-S equation with dp/dt transient combustion model and k-ε turbulent model. The pressure-time p-t curves and heat transfer status inside solid propellant were both obtained simultaneously. Compared with the test result,it is showed the transient model used in the numerical simu-lational is suitable for the phenomenon here.