Abstract: A rapid cycling synchrotron (RCS) with a 7 MeV linac has been under construction. The negative hydrogen ion beam H- beam injected into RCS adopts the multi-turn charge exchange injection scheme. The stripper foil system which is able to replace detective foils and adjust foil position accurately in vacuum is needed. This paper presents a foil exchange system based on steel belt transmission for its high accuracy and stability. By calculating cross section, we can estimate the stripping efficiency according to particle kinetic energy and give appropriate foil thickness. Foil temperature rise and stress which are the main reasons leading to foil rupture are analyzed using finite element method and the lifetime model is combined with experiments to predict foil lifetime of our program. The stripping efficiency reaches 99.0% when the foil thickness is 40 nm. The maximum temperature point of the foil is 755.5 K. In conclusion, the mechanical system and foil property satisfy the project requirement.