By means of Kane's method the dynamic equations of passive controllers on rock- et launchers are introduced. The real system of the passive controllers is simplified to a twelve degree-of-freedom system model. The relative angular velocities are selected as gener- alized speeds to obtain the partial angular velocities and partial velocities. Generalized inertial forces and generalized active forces are discussed. The dynamic equations using tensor/ma- trix expression are formulated. The dynamic equations has been solved on a M-24OD com- puter in the Province Computing Centre of Shanxi. The calculating results are identified with the experimental results.