The invention relates to a delaying spring assembly for a vehicle seat. The delaying spring assembly comprises a sliding plug cylinder and a cavity spring, wherein the cavity spring is jointly abutted in the middle part of the cavity spring by an upper plug cap and a lower plug cap, a plug rod arranged at the upper part of the upper plug cap extends out of the upper end of the sliding plug cylinder, and a plug rod arranged at the lower part of the lower plug cap extends into a guiding hole in the lower part of the sliding plug cylinder; the cavity spring is provided with an upper cover and a lower cover which are mutually buckled, a spring is arranged in a cavity jointly formed by the upper cover and the lower cover, and one or more air holes are formed in the upper cover or the lower cover. The cavity spring needs to enable gas to flow in and out from a wedge-shaped hole in a contracting process and an extending process, the process for air to flow in and out needs time, because of the atmospheric pressure in the cavity, and the vibrational frequency of the cavity spring is decided by the atmospheric pressure and the nature of the spring instead only by the nature of the internal spring, so that an unfixed frequency can be coupled newly by the cavity spring and the spring connected with the lower plug cap under the cavity spring, the vibrational frequency is reduced, resonance cannot be caused, and a long-term uncomfortable vibrational frequency can also not be caused for a human body.