Abstract: By introducing the trapezoidal median line theorem, the relationship between forces is clearly expounded with geometric figures and Hooke’s law.The concept of effective tension release coefficient H_α is proposed, the conventional factor K₁ is defined, and a calculation method of maximum effective tension is provided.The applicability and accuracy of H_α are proved by the proportional coefficient X_α.The comprehensive performance curve is drawn.Under the change of belt-speed, the variation laws of tight edge limit tension F₁,loose edge limit tension F₂,maximum effective tension F_ec and maximum power P₀ are discussed.The curve of maximum stress and power is given, the selection method of optimal belt-speed is clarified, the calculation method of maximum power P₀ under any envelope angle α₀ is given, and the safety factor S₀ is defined.