The invention discloses a passive safe cooling system. The system comprises a water replenishing tank, an advanced safe filling tank, a built-in material replacing water tank, a pressure releasing system, a passive emergency water supply system and a passive safety shell cooling system, wherein the water replenishing tank, the advanced safe filling tank, the built-in material replacing water tank and the pressure releasing system are all arranged inside a safety shell and respectively communicated with a pressure container; the passive emergency water supply system hermetically penetrates through the safety shell, corresponds to a steam generator arranged inside the safety shell and is used for realizing water supply reflowing and heat output of the steam generator; the passive safety shell cooling system hermetically penetrates through the safety shell so as to output the heat out of the safety shell. Without intervention of a passive system and an operator, the passive safe cooling system disclosed by the invention can be used for effectively realizing safety functions such as reactor core reactivity control, afterheat output and radioactive substance containment under accident conditions and ensuring that a reactor core can be cooled effectively and maintained in a safe shutdown state, so that the safety of a nuclear power station is improved and the building cost and operating cost of the nuclear power station are also greatly lowered.