The utility model discloses a valve deck, a valve assembly and a refrigerating system. The valve deck comprises a side wall, a closed end and a sealing part, wherein the closed end is connected to the side wall, and an internal space is defined by the closed and the side wall; the sealing part extends into the internal space from the closed end, and at least one portion of the sealing part can extend into an opening of an external valve body and is sealed on the internal surface of the valve body; a gap is defined by the sealing part, so that internal pressure in the gap enables the sealing part to be tightly attached to the external valve body. The valve assembly comprises the valve body and the valve deck. The refrigerating system comprises the valve assembly. The valve deck, the valve assembly and the refrigerating system can improve the sealing effect.