The wellbore injected with heating fluid requires temperature field prediction to formulate production strategy. The classical radial heat transfer calculation of wellbore takes into account the thermal conductivity resistance of casing, cement sheath and formation, ignoring the "Thermal Contact Resistance" caused by the micro-annulus at the cementing interface. In order to study the influence of micro-annulus on radial wellbore temperature field prediction, the calculation method of thermal contact resistance of micro-annulus at the cementing interface filled with gas was deduced. And then it was verified by the experimental equipment and specimens of casing, cement sheath and formation. Finally, the thermal contact resistance was introduced into the "overall heat transfer coefficient" to study the deviation of the classical method in predicting the wellbore temperature field. The results show that, if the interfacial thermal contact resistance isn't considered, under the conditions of the roughness of micro-annulus increases (0.01 mm similar to 1 mm), the time of steam injection increases (2 d similar to 40 d), the temperature of injected steam increases (500 K similar to 700 K), and the temperature of formation increases (300 K similar to 400 K), the calculated inner wall temperature of the cement sheath will be relatively high (1 K similar to 3 K), and the outer wall temperature will be relatively low (4 K similar to 9 K), while the inner wall temperature of the formation is relatively much high (28 K similar to 38 K). Moreover, the change of these conditions has little influence on the deviation. The research in this paper proves that the micro-annulus at the cementing interface has a great influence on the radial wellbore temperature prediction. The calculation method used can make the prediction more in line with the actual situation, thus making the production dynamic analysis and method optimization more effective.