In this paper, with 1000 kg of oil shale for research, the heat and material balance of Myanmar oil shale processing by Sanjiang gas combustion rectangular retort (SJ-retort) was calculated. The results show that the heat requirement of Myanmar oil shale retorting can be satisfied by its high-calorie retorting gas combustion as well as the heat release from the retorting process. In the study, 33.26% surplus retorting gas is obtained, which indicates that the Myanmar oil shale processing by SJ-retort is theoretically feasible. In addition, a concise, and accurate method is proposed to calculate the gas balance of the retorting process, which can calculate the dynamic equilibrium value of various types of gases (total input and output gases, recycle gases, and the new air that enters the retort) when the retorting system reaches a steady state. This method was validated with the successful operation of a pilot-scale test for oil shale retorting in Shenmu of Shanxi province and Yaojie of Gansu province in China.