Abstract: Aiming at the transmission device beam problem appeared in the 10th National Chou Peiyuan College Mechanics Competition, a relatively accurate stress solutions were given by using the elastic mechanical system based on the stress boundary conditions. Considering the influence of shear distortion effect on the stress component, the similarities and differences between the present solution and the official answer were compared, and the torsional stress correction term was derived by further considering the comprehensive effect of transverse and tangential loads. Results show that the complete function of the correction term derived by expressing the longitudinal displacement of the beam as the separated form of the longitudinal and abscissa functions is consistent with the elastic solution. The span-to-height ratio has a significant influence on the distortion effect. It is completely reasonable within the scope of slender beams according to the offical answer, and the expanded solutions in this paper will help deepen the understanding of the knowledge system of material mechanics.