The invention provides a method and equipment for quenching and cooling a thick-walled steel pipe. According to the method, a quenching and cooling steel pipe is placed on a material rest, the material rest is arranged in an inner tank, and the inner tank is placed at the internal upper part of an outer tank; and during liquid immersion, liquid is pumped out of the outer tank by a pump and injected into liquid spray devices which are arranged at the two sides of the quenching and cooling steel pipe of the inner tank, the liquid is sprayed to the quenching and cooling steel pipe from spray holes, facing to the quenching and cooling steel pipe, of the liquid spray devices, and meanwhile, the liquid level of the inner tank rises along with the increase of the liquid in the inner tank until the quenching and cooling steel pipe is fully immerged into the liquid, so that the liquid immersion cooling is realized while the spray cooling is realized. The equipment comprises a quenching and cooling steel pipe external wall liquid spraying and immerging system, a quenching and cooling steel pipe internal wall cooling liquid injection system and a quenching and cooling steel pipe internal wall cooling liquid draining system. The method and the equipment have the advantages that the structure of the equipment is simplified while the situation that the internal and external walls of the quenching and cooling steel pipe are uniformly cooled at high cooling intensity is guaranteed, and the reliability of the operation of the equipment is improved.