The invention provides a cushion of a seat and belongs to the field of necessities for human life. The cushion solves the technical problems that the existing cushion of the seat has a poor effect of adjusting coldness and heating and the like. The cushion of the seat comprises a support frame, a first spongy cushion with air holes, a jacket with air holes and a fan, wherein the first spongy cushion is arranged on the support frame; the support frame and the first spongy cushion are coated with the jacket; a platy air deflector and a ventilation layer with meshes are arranged between the support frame and the first spongy cushion; an air guide groove distributed on the air deflector is formed in an upper plate surface of the air deflector; the upper plate surface of the air deflector is fixedly covered with the ventilation layer; an air outlet of the fan is communicated with the air guide groove via a ventilation pipeline; an air outlet channel for the fan to drive air to flow is formed among the ventilation pipeline, the air deflector, the ventilation layer, the first spongy cushion and the jacket; and a heating component is arranged in the air outlet channel. The cushion has the advantages of uniform cooling or heating of the surface of the cushion under the condition of ensuring comfort of the cushion.