Abstract: Aimed at a new process for rough preparation of composite long truss-stack slippage process, the me-chanical performance test matrix related to the limit parameter of the stack slippage process was made. The effects of stack slippage process on the tensile properties, compression properties, bending properties, shear properties of short beams, opening-hole compression properties and internal shear properties of M21C laminates were studied. The experimental results show that the stack slippage process has no effect on the opening-hole compression performance of the M21C laminates, and the tensile properties, compression properties, bending properties, shear properties of the short beams and the internal shear properties will decrease to a certain extent.