Core contents of the method: First, credit evaluation system, from 5 dimensions of maintenance quality, emergency disposal, compliant operation, complaints and reports, accident responsibility, set 28 evaluation indicators, conduct annual credit scoring for maintenance units, divided into four grades: A (excellent), B (good), C (average), D (poor); Second, red and black list identification, maintenance units with grade A for 2 consecutive years, no illegal acts, zero safety liability accidents are included in the red list; those with 8 types of situations such as false maintenance, unlicensed operation, safety liability accidents, refusal to rectify hidden dangers are directly included in the black list; Third, hierarchical supervision measures, reduce the inspection frequency for grade A units, and give priority to recommending them to participate in government procurement projects; list grade D units as key supervision objects, inspect no less than once a month, restrict participation in government procurement and bidding projects, and publicize illegal information to the society; Fourth, joint punishment mechanism, black list enterprise information is pushed to housing construction, development and reform, finance and other departments, and restrictions are imposed in qualification review, credit financing, bidding, etc. Those listed in the black list for 2 consecutive years will have their special equipment operation license revoked; Fifth, credit repair mechanism, enterprises listed in the black list can apply for credit repair after completing rectification and eliminating adverse effects. After the repair is passed, they will be removed from the black list and the punishment measures will be lifted.