The initial alignment error would produce the auto-control termination of sub-launched missile. Based on the theoretical analysis, deduces a simplified algorithm to calculate the impact of the initial alignment errors on auto-control termination errors of sub-launched missile weapons. Finally, the numerical results calculated by the simulation with the initial alignment data of the sub-launched missile. The simulation results show that the model is simple, pellucid and wieldy, avoids fussy calculation and provides academic foundation of allotting the initial alignment error index without enough missile data support in the project verification phase.