A novel multivector coarse alignment method of laser SINS in inertial frame is proposed to solve the problem that it is difficult to achieve coarse alignment because of the motion jamming of vehicles on swaying bases. The principle and shortcoming of doublevector based inertial coarse alignment are analyzed, and the alignment model based on multivector is established. Finally, the simulations are conducted to verify the new method, which show that compared with the traditional method, the proposed algorithm can effectively eliminate the influence of motion jamming by fully taking advantage of the measurement data. As a result the DCM matrix can be acquired with better accuracy and stability.