Abstract: In order to solve the problems of difficult chip breaking and difficult chip removal in deep hole drilling of oxygen-free copper, an experimental study on gun drilling of multi-hole TU1 oxygen-free copper was carried out based on the response surface analysis method. Feed rate, cutting speed and cutting fluid pressure were used as input variables. Meanwhile, the gullet-to-chip area ratios and chip deformation coefficient were set as the response values. The regression model between the input variables and the response values was established to obtain the combination of optimized parameters. The results show that the effects of single factors on the gullet-to-chip area ratios and chip deformation coefficient are in the order of feed, cutting speed, and cutting fluid pressure; the interaction of cutting speed and coolant pressure has the most significant effect on the gullet-to-chip area ratios and chip deformation coefficient in the multifactorial interaction. When the feed is 0.023 mm/r, the cutting speed is 47.1 m/min, and the cutting fluid pressure is 2.1 MPa, the C-type chips obtained are ideal chips with smooth chip removal. This paper provides a theoretical reference for the selection of process parameters for deep hole drilling of easy-to-cut large deformation materials.