The utility model relates to a compact pressurized water reactor, including main pump, steam generator, pressure vessel to and intercommunication steam generator and pressure vessel's a double casing pipe structure, intercommunication main pump and steam generator's the 2nd double casing pipe structure. A double casing pipe structure includes first passageway, the second channel of mutual isolation, the 2nd double casing pipe structure includes third passageway, the four -channel of mutual isolation, feeds through between main pump, steam generator, the pressure vessel, forms the circulation circuit of working medium. Adopting the double casing pipe structure between each main equipment, having reduced the distance between each main equipment, makes small -size heap of structure compacter, a loop system's trunk line length has been shortened in the design of the whole support of being convenient for by a wide margin, has reduced the heat loss of main cooling agent in a loop system cyclic process, makes a whole loop system compacter. Reactor with the double casing pipe structure can wholly lift by crane the installation, relative raft subset take one's place respectively and last welded mode high -efficient swift.