Abstract: According to the study of heavy oil thermal recovery casing damage mechanism, two casing damage prevention computation theory of pipe string pulling up prestress and casing thermal compensator are made. Simulation results show that: when set pulling up prestress, the minimum pulling prestressed needed for pulling pipe string and minimum tensile length increased firstly, then decreased with the increasing of pipe string temperature; when using the casing thermal stress compensator, the required minimum compensation increased with the increasing of pipe string temperature and length, but the increasing tends slow. The computation theory can be used to guide the thermal recovery wells casing damage prevention design and construction work.