Aiming at the problem of evaluating the quality of the pile body accurately based on the temperature field of the hydration heat of the cast-in-place pile，we use the characteristics of the concrete hydration heat temperature changing approximately linear with radial distance (from the center of the pile cross-section) within the range of the radial distance greater than 0.5 times the pile radius，and build the method for calculating the deviation of the reinforcement cage based on the temperature of two symmetrical measuring points on the reinforcement cage.Combining with the simulation analysis of the hydration heat of the defective pile，we systematically analyze the influence of the geometric characteristics of the defect and the change of thermal parameters on the temperature field，and propose the method for judging the presence of defects and analyzing their spatial distribution position based on the characteristics of the temperature-depth curve obtained from temperature measurement points along the main reinforcements.Combining field tests and comparison with low-strain and cross-hole ultrasonic testing results，we verify the feasibility of the method.