The reason why the people why must be the good safety belt and use auto safety envelope system during riding was caculated and analyzed by applying the scientific momentnm theorem, which strengthen the poople s security and make the people learn how to protect themselves during riding.

The analysis of the fault in the safety belt caused by the frontal crashes of the real vehicle shows how the safety belt protects a driver in accidents.

Function of seat belts in automobiles as well as injury to drivers and passengers by impact during collision are analyzed, the passive security function and protection effect of seat belts are analyzed, fundamental maintenance knowledge of seat belts is introduced.