Abstract: At present, it is in urgent need to dispose the abandoned pipelines in Northeast China in a safe and environmentally friendly way, and it is quite significant to clean the residues inside the pipelines completely. Therefore, it is proposed to adopt the cleaning technology which combines pigs and chemical cleaning agents. So far, however, this technology has never been applied to any onshore abandoned pipeline and no operation process is available for engineering application in China. In this paper, the general application principles and operation process requirements for the application of this combined cleaning technology were analyzed based on the characteristics of abandoned pipelines after the basic theories of combined pipeline cleaning were investigated. Then, simulation testing was performed on the dissolution effects of the chemical cleaning agents on hard wax to verify the effectiveness of chemical agents. And finally, field experiments were conducted on the mothballed old pipelines in Northeast China to demonstrate the practical performance of combined cleaning technology in abandoned pipeline disposal engineering, so as to promote the development of its operation process and provide the basis for its popularization and application to the disposal of abandoned pipelines. It is shown that based on this combined cleaning technology, the residues inside the pipelines can be well cleaned and the safety and environment risks related with abandoned pipelines can be eliminated, so it is an important safety technology for the disposal of onshore abandoned pipelines.