Abstract: The thermal pipeline is generally arranged in the center of the city, and the leakage accident has a great social impact. In order to reduce the industrial and social safety hazards during the heating period, a safety assessment method is proposed for the thermal pipeline during the non-heating period to improve the safety level of the thermal pipeline. The article introduces the principle of weak magnetic detection technology and the evaluation method of pipeline damage degree. The damage degree of pipeline was evaluated in the field test, and verified by transient electromagnetic method, and then verified by excavation. The field verification results show that the weak magnetic detection method can be used to quickly locate the suspected corrosion area of the thermal pipeline, and then the transient electromagnetic method is used to verify the severity of the corrosion point, which can realize the safety evaluation of the thermal pipeline. The defect quantitative error is not more than 20%.