Abstract: In the special underground project, there are no free surfaces on the cement. The ultrasonic transducers which are used for strength measurement are filled in the cement directly. The early strength is tested at the internal temperature of 40-90 ℃ which is different from the calibration temperature in the lab.The ultrasonic velocity will be influenced by the temperature inside cement, then the strength of cement will be so. In order to solve this problem, the method of simulating temperature environment inside cement is adopted. The result indicates that the precision of testing has been improved by this method.