Abstract: The shut-down and restart-up tests at different conditions aimed at Daqing crude are done on the wax deposition simulation loop in the laboratory. In the tests, the strengths of wax deposition layer formed at different shut-down conditions are investigated. The test results show that the strengths of wax deposition layer formed at different shut-down temperatures have obvious differences and the strengths of wax deposition layer formed after shut-down increase with the shut-down time.