The invention relates to a reactor core molten debris grouping retention and cooling system which comprises a grouping retention system and a cooling system. The grouping retention system comprises a molten debris retention vessel loading shaft arranged at the bottom of a reactor cavity and multiple molten debris retention vessels arranged in the molten debris retention vessel loading shaft, the molten debris retention vessels are connected with the reactor cavity through multistage molten debris transport channels, molten debris retention vessel transfer devices are arranged on the molten debris retention vessel loading shaft in a penetrating mode, and the molten debris retention vessel transfer devices are connected with the cooling system; the cooling system comprises a molten debris cooling water tank and a cooling circuit of the molten debris cooling water tank. The reactor core molten debris grouping retention and cooling system aims at achieving grouping retention and cooling on reactor core molten debris by means of an independent packaging container on the working condition that serious accidents occur; improvement of molten debris decay heat exporting power is facilitated, and an irradiation dose to a worker is reduced; the structure is compact, and the occupied space is small.