Test and evaluation on the reinforcing bar damage of concrete in fire are important aspects on the fire damage evaluation of concrete structures.According to the electrochemistry testing principle of the reinforcing bar corrosion,three elements of electrochemistry were applied to study the reinforcing bar damage of concrete in fire.The electrochemistry criteria and auxiliary(analysis) models were established by experiments.The reinforcing bar damage of concrete in a real fire was diagnosed and evaluated using above criteria and analysis models.