Abstract: Considering the complexity of the dynamic load calculation using the multidegreeoffreedom model for the hoisting system of the excavator， initially， the driving parts of hoisting system， such as axle， gear， coupling and structural parts， were taken as rigid component， only left the hoisting wirerope taken as elastic component without taking the damping effect into consideration. A twodegreeoffreedom model was put forward by simplifying the multidegreeoffreedom model for excavator’s hoisting system. Under the lockedrotor conditions where arm is perpendicular to the movable arm and the bucket rod is completely out of position， the dynamic load coefficient of the hoisting system was calculated by the Lagrange equation method， and compared with the coefficient from the multidegreeoffreedom model. The result shows that the twodegreeoffreedom model can be used instead of the multidegreeoffreedom model to simplify the calculation in the preliminary design stage.

Key words: excavator, dynamics, vibration, hoisting system, dynamic load