In order to meet the requirements of surface roughness, upper port size precision and material removal rate of the bottom of monocrystalline silicon microgroove in practical application, the processing method selects fine milling, and the above three evaluation indexes are optimized by gray correlation analysis (GRA). Firstly, by designing the orthogonal test, the predicted value of the evaluation index is obtained, and the relationship between each index and the process parameters is analyzed. Then the grey correlation method is used to calculate the grey correlation coefficient of each evaluation index of the test sequence, and then the grey correlation degree of each test sequence is ranked, so as to obtain the best combination of process parameters, and many experiments are carried out to verify its feasibility, so as to improve the processing quality and processing accuracy of the microgroove.