Abstract: In order to investigate the influence of high temperature and copper slag fine aggregate on corrosion mode of steel bar in concrete, high temperature test was carried out on concrete specimens with different copper slag replacing ratios, then the artificial accelerated chloride ion corrosion test was conducted on the specimens using dry-wet cycling immersion method, and the corrosion state of steel bars embedded in concrete was monitored by measuring the half-cell potential value using electrochemical method, the chloride ion content in concrete and corrosion rate of steel bar were also measured at last. The results show that the half-cell potential method well reflects the actual corrosion situation of steel bar in specimen. High temperature destroys the chloride ion penetration resistance performance of concrete, thus causing the corrosion degree of steel bar in concrete specimen increases with the increase of heating temperature. In addition, the combined effect of inherent larger expansion deformation of copper slag at high temperature and uncoordinated shrinkage between copper slag and cement paste after cooling furtherly destroys the microstructure of concrete, thus causing the corrosion rate of steel bar increases with the increase of copper slag replacing ratio. A fitting formula for corrosion depth of steel bar in copper slag concrete after exposure to high temperature under chloride attack was established at last.