To study the feasibility of double-curved PDM into casing, the mechanical model of Φ172 mm double-curved PDM into Φ244 mm straight casing is established. The effect of different structure corners on the feasibility is analyzed for the PDM into casing; and the law of stress distribution is discussed in the paper. The simulation results show that the Φ172 mm double-curved PDM can enter Φ244 mm straight casing favorably by self-gravity when the first structure bend is equal to 1° and the second structure bend is equal to or less than 1.5°. When the second structure corner is equal to or more than 1.75°, PDM needs extra to enter into casing. Within the bounds of common structure corners,when the PDM into casing, the maximum stress value of the double-curved PDM is much lower than yield strength.