Incomplete contact at solid interface will produce thermal contact resistance. In order to study the influence of microcracks on wellbore temperature field prediction, a set of experimental equipment was designed and built to investigate the thermal contact resistance between formation and cement sheath, cement sheath and casing. The theoretical calculation method of thermal contact resistance deduced was verified by experiment, and the influence of ignoring cementing interface thermal contact resistance on prediction accuracy of wellbore temperature field was studied. The results show that, the relative error of thermal contact resistance measured by the equipment at 30~300℃ is less than 9.28%; The theoretical calculation method is related to the spacing and temperature of surfaces. If the interfacial thermal contact resistance is not taken into account when predicting the wellbore temperature field, when the width of microcracks increases (5×10-5m~1×10-3m), the time of steam injection increases (2d~40d), or the temperature of formation increases (305K~400K), the calculated outer wall temperature of the cement sheath will be relatively low (about 3K), while the inner wall temperature of the cement sheath and formation will be relatively high (about 14K). Considering the thermal contact resistance of the microcracks at the cementing interface can improve prediction accuracy of the wellbore temperature field.