As important ingredients in corrosion inhibitor at high temperature acidizing，pyridine quaternary ammonium salt and antimony salt have been universally used in application. In this paper，chemical soaking at high temperature and high pressure and electrochemical measurements was carried out to investigate the synergistic corrosion inhibition effects between pyridine quaternary ammonium salt（BDJ）and Sb₂O₃ on N80 steel in 20%HCl solution. The performance of the formed film at different conditions was analyzed using contact angle，scanning electron microscopy（SEM），energy dispersive spectroscopy（EDS），X-ray diffraction （XRD）and attenuated total reflectance（ATR）. The mechanism of film forming process of acidizing corrosion inhibitor relating BDJ and Sb₂O₃was proposed. The results showed that there existed in apparent synergistic corrosion inhibition between BDJ and Sb₂O₃. With the increase of Sb₂O₃concentration，the inhibition efficiency was remarkably enhanced. When adding corrosion inhibitor of 2% BDJ + 0.5% Sb₂O₃，the corrosion rate of N80 steel decreased to 18.0 g/（m²·h），which was far less than the requirement of 45 g/（m²·h），as a result，the inhibition efficiency increased over 95%. The mixture inhibitor shifted the potential positively and decreased the corrosion tendency thermodynamically. The protective film was consisted of compound film with Sb and BDJ inside，which effectively enlarged the contact angle and inhibited the acid corrosion.