The present disclosure provides a reinforcing part for a speaker diaphragm, a diaphragm and a speaker. The reinforcing part is an overlapped three-layer structure and comprises a support layer as well as a first heat dissipation layer and a second heat dissipation layer that are fixed and bonded on surfaces of two sides of the support layer respectively, the support layer comprises through holes penetrating surfaces of two sides thereof, and the reinforcing part further comprises fillers located within the through holes and configured for heat conduction, the fillers having thermal conductivity higher than that of the support layers.