Abstract: To address the issue of inefficient and inaccurate pose control caused by coupled errors in spatially constrained heavy-load dual-pendulum platforms, an error modeling and compensation method based on the rigid body motion assumption is proposed. The error formation mechanism of coupled errors for pitch and roll angles is analyzed, considering manufacturing processes and assembly relationships. The key geometric error parameters affecting pose control accuracy are identified, and the kinematic model is refined. A coupled error model is established based on mechanical relationships, and the distribution characteristics of both independent and coupled errors are analyzed through numerical simulations. A compensation strategy and related methods for pose errors are proposed. The effectiveness of the error compensation model is further validated using a uniform experimental design method. Experimental results demonstrate that the error compensation method based on the geometric error model significantly improves the accuracy and efficiency of pose control. This study provides a theoretical foundation for the design and manufacturing of heavy-load dual-pendulum platforms under spatially constrained conditions.