Abstract: In order to optimize the atmospheric pressure micro-plasma jet etching process with the beam spot diameter in the micron level, an atmospheric pressure micro-plasma jet device with simple structure and convenient operation was built. Taking typical polymer parylene-C film as the research object, the etching process of parylene-C film treated by atmospheric pressure micro-plasma jet was studied, and the influences of process parameters such as O₂ flow, working voltage, working distance and etching time on the etching line width and etching depth were analyzed. The results show that the etching line width and etching depth can be increased by increasing the O₂ flow, working voltage, working distance and etching time. With the continuous increase of the above process parameters, the etching line width and etching depth do not increase significantly, even decrease. The working voltage and working distance have a great influence on the etching effect of parylene-C film, and play a key role in the etching process, and the controllable adjustment of the polymer etching process can be realized by adjusting these two parameters.