Abstract: In response to the technical requirements of the "Tianyuan-1（TY-1）" micro/nano satellite formation flight mission，the overall design of the micro propulsion system was carried out.Due to low specific impulse，high storage pressure and complex structure，the conventional cold gas propulsion is difficult to meet the requirements of micro/nano satellites.R134a was chosen as the propellant，and by liquefying the propellant the propulsion system volume can be reduced effectively.Based on the 3D printing technology，the storage tank，plenum chamber，and the pipe can be integratedly designed.To improve the system specific impulse，the heating nozzle was designed and manufactured by using MEMS processing technology.The thrust and specific impulse were analyzed under different nozzle sizes，gas pressure and jet temperature.Based on the analysis result，the nozzle design was confirmed.The heating nozzle characterization test shows that the error of manufacture is controlled under 2%.Under vacuum conditions，the thrust performance was tested by using torsion pendulum measuring system.The results show that this propulsion will produce thrust between 5 and 10mN if the pressure is controlled between 0.1MPa and 0.2MPa.Besides，the specific impulse will increase by 10% if the jet temperature is raised from 25℃ to 95℃.

Key words: formation flying, cold gas micro propulsion, MEMS processing technology, increase specific impulse, thrust test, system design