In the deep hole drilling process of TC4 titanium alloy, due to high drilling temperature and long chip removal path, the tool wear was aggravated, which affected the quality and accuracy of deep hole. In order to establish the processing parameters for deep-hole drilling of TC4 for actual production process, the gun drilling experiment of TC4 titanium alloy was carried out. The results indicated that drilling temperature was greatly affected by drilling speed, and the influence of feed rate was not significant. Deep-hole diameter and roundness increased with the increase of drilling speed, the co-axiality increased firstly and then decreased with the increase of drilling speed. Surface roughness of deep-hole increased with the increase of drilling parameters, surface quality of deep-hole was further deteriorated under large drilling parameters. Work hardening layer of each group was about 30μm, and with the increase of drilling speed, extrusion deformation of the chip was more serious. After the comprehensive analysis, drilling speed was 20m/min, feed rate was 0.08mm/r, which were the optimum processing parameters of TC4 titanium alloy deep-hole gun drilling under dry conditions.