The invention relates to a thick plate and extra-thick plate quenching experimental device and a method. The device comprises a quenching tank, a transmission device, a feeding device, a centering device, inclined tracks and a transport trolley; the transmission device, the feeding device and the centering device are hinged at one side of the quenching tank with pins after being integrated, and can be folded into the quenching tank after being turned over; the inclined tracks are arranged in the quenching tank, with the top close to one side of the pins; the transport trolley can be lifted and moved in the quenching tank along the inclined tracks, and a horizontal specimen holder is arranged on the transport trolley. The experimental device provided by the invention has the advantages of simple structure, high carrying capacity, high applicability, high automaticity, and low operation and maintenance cost, can be used to finish quenching experiments of thick plates and extra-thick plates effectively, and is beneficial to improving the hardenability and quenching accuracy and reducing the labor intensity.