Abstract: HGCJ-20 bar tensile impact specimen machining center can realize one-step processing and forming of impact specimen. In order to maintain the neutrality and fixity of impact specimen, it is necessary to drill a pin hole at one end of it. Through the impact test of the impact standard specimens and the impact processing specimens of 42CrMo steel and Q235H steel after different drilling, the influence of the pin hole and its depth on the impact absorption energy test value of the impact specimens and the influence of HGCJ-20 bar tensile impact specimen processing center and traditional processing technology on the impact absorption energy test value of the impact specimens were compared. The results show that for 42CrMo steel and Q235H steel, the average value of the impact absorption energy of the impact specimens processed by the new machining center with the pin hole depth of 5 mm was the same as that of the impact specimens processed by the traditional technology. For the impact standard specimen and Q235H steel, when there was no pin hole at one end of the impact specimen or the depth of the pin hole was not more than 8 mm, the measured average value of impact absorption energy was stable and fluctuated in the normal range (110-120 J). When the depth of the pin hole reached 9 mm and was higher than this value, the measured average value of impact absorption energy of the impact specimen was generally lower than the normal range.