An apparatus for retention of molten material for a Generation IV reactor after a nuclear power plant accident comprises an inner wall which is peripherally closed, a vapor channel wall with an opening at the bottom fixed in the inner side of the inner wall, a pressure vessel disposed in the vapor channel wall, a vapor rising channel formed between the pressure vessel and the vapor channel wall, and it further comprises an outer wall surrounding the inner wall, a core molten material retention apparatus fixed at the bottom of the inner wall, and a deflector keeping away from the inner wall and the core molten material retention apparatus to form a gap; wherein a coolant falling channel is formed between the outer wall and the deflector, a coolant inlet is disposed at the bottom of the deflector, and a coolant channel is disposed between the inner wall and the core molten material retention apparatus; a core molten material retention recess is disposed at the upper surface of the core molten material retention apparatus, and the lower surface of the core molten material retention apparatus is arch-shaped; the core molten material retention apparatus is made of non-metal inorganic fireproof material. The invention adopts the design of molten material retention outside the reactor, using different material containing molten material and cooling the molten material by coolant cycle and the deflector structure, thus to improve the safety of the nuclear power plant.