Abstract: A technical scheme for coaxial transmission of microwave energy based on oil drilling tools is proposed, which transmits the electromagnetic energy from the ground to the downhole. The propagation characteristics of microwaves in the coaxial transmission structure composed of oil drill pipes and casings are analyzed, and the optimal combination of drilling tools suitable for microwave energy transmission is selected according to petroleum industry standards, and HFSS simulation verification is carried out. The simulation results show that the coaxial line composed of 2^3/8″ in the API standard oil drill pipe and 5^1/2″ in the standard oil casing has the best transmission efficiency. Through the comparative analysis with the actual operating parameters of conventional thermal oil production technology in a heavy oil reservoir in China, it is confirmed that the proposed microwave energy transmission scheme is feasible and can be used for the transmission of downhole microwave energy.