The invention discloses a system for passive cooling and water supplement of a spent fuel pool. The system comprises one or more groups of heat pipe loops and one or more groups of water supplement pipes, wherein one end of each heat pipe loop is accommodated in the spent fuel pool; the other end of each heat pipe loop is accommodated in sea water or river water outside the spent fuel pool; a heat-conducting circulation channel is formed in each heat pipe loop; one end of each water supplement pipe penetrates through the spent fuel pool in a sealed manner; the other end of each water supplement pipe is communicated with the sea water or river water outside the spent fuel pool. The heat pipe loops can transfer heat in the spent fuel pool to the sea water or river water in a passive manner, so as to achieve long-term after-heat removal from the spent fuel pool; when the water level in the spent fuel pool is lowered due to an accident condition, the water supplement pipes can supplement water to the spent fuel pool in a passive manner; therefore, the system provided by the invention needs not to be maintained by power, and thus the situation that the system is unavailable due to a power-loss accident can be avoided; the system is high in reliability, and particularly has strong protective capability under a comprehensive power outage condition, so that the safety and economic efficiency of a nuclear power plant can be improved; besides, the system is simple in structure.