At present, the middle-deep shale gas in south Sichuan province has entered a large-scale development stage, and a complete and mature production gathering and transportation system has been established from the mountain cluster wellhead platform to the dehydration station for processing. Laboratory analysis has been conducted for the insoluble impurities in triethylene glycol solution and TEG regeneration system of dehydration station in Zijinba block, at different production stages. The test results were compared with the fault diagnosis of Triethylene Glycol Dehydration System in operation. It is found that the backflow fluid from gas well into TEG regeneration system is the main factor causing scaling in dehydration unit; the impurity in triethylene glycol solution is different at different production stages, and the consequences of failure is different; different processes used in gas well development will pose different effect on the dehydration system. The study considered that keeping the triethylene glycol in the circulation system in a relatively pure state in the natural gas dehydration system is the key factor to ensure the normal operation of natural gas dehydration unit. The adoption of process optimization, improvement of production equipment and enhancing maintenance system can well prevent the adverse effects of shale gas backflow on natural gas dehydration unit at different production stages and ensure the normal production of natural gas dehydration stations.