Abstract: Using the instantaneous detonation assumption and linear approximation of tiny charge mass, the impulse and thrust of a micro-detonation thrust unit operating in vacuum are theoretically calculated. Based on this, the influences of specific detonation heat, isentropic exponent and length of the nozzle on the impulse and the thrust are studied. Furthermore, by numerical simulation, the time-dependence of the pressure on the end of nozzle is obtained, and the variation of impulse provided by the micro-thruster with the length ratio of nozzle to energetic material is also investigated. The results showed that increasing the charge mass, the isentropic exponent and the specific detonation heat can enhance the impulse of a thrust unit, and the nozzle length must be over 4 times of the charge length to achieve the perfect propulsion performance.