In order to improve the usability of PRTH (portable rope-track hoist), the friction-based PRTH lifting capacity was studied. The influence of tension at the end of the rope, wrap angle and relative size on the friction between the wheel and the rope was experimentally studied by using the control variant method. The results show that: the friction increases with the increase of the three factors, but the trend is slowed down; the coefficient of static friction decreases with the increase of the end tension and the wrap angle and tends to be stable, and it increases with the relative size of the wheel to the rope and converges to a constant. The effects of wrap angle and end tension on the friction were demonstrated to be identical to each other, the size effect of wheel-rope friction was found, and a new lifting capacity model on wheel-rope friction was established with the three factors. The model is the sublation of Euler formula, deepens the understanding of the friction law between the wheel and the rope, and is of great significance to the miniaturization and lightweight design of PRTH.