Abstract: According to the thoughts of the system theory， taking the driving moment of hoisting system as generalized force， a dynamic model of elastomer and rigid body with many freedom degrees for hoisting system was established using the dynamic theory and Lagrange equation method. The vibration response of hoisting system was calculated based on the matrix iterative method under conditions of locked rotor and vertical boom spreading of bucket rod. The calculated dynamic load coefficient of the highspeed shaft and the hoisting rope is 1343 and 1374， respectively. The effects of lockedrotor time and soil stiffness on the dynamic load of hoisting system were analyzed and accordingly the dynamic load coefficients with different soil stiffness were obtained. To reduce dynamic load and ensure the safe functioning of device， the lockedrotor time should not be more than 20s.

Key words: excavator, dynamics, dynamic load, vibration, matrix iterative method