The work aims to study the relevant calculation theory of conveying motion and telescopic motion of multi-section telescopic loader to facilitate the selection of key components and ensure the correctness of the selection. Based on the structure of telescopic loader and combined with the relevant existing research theories, the components of the circumferential force of conveyor belt driving drum of multi-segment telescopic loader were analyzed, and the calculation method of the circumferential force of conveyor belt driving drum was obtained. Based on the principle of telescopic motion of frame, the force analysis of telescopic parts of telescopic loader at all levels was carried out, and the calculation method of telescopic driving force was obtained. Taking the product of a telescopic loader as an example and combined with the simulation results of SolidWorks motion module, the calculation method was verified. The results showed that, the power of the driving motor calculated by the circumferential force and the telescopic driving force of the conveyor belt driving drum was the same as that of the product. The calculation method of parameters related to conveying motion and telescopic motion of telescopic loader is feasible and the results are correct. It has certain reference value in the research of telescopic loader.