Provided is a method for hybrid welding of a high-strength bridge steel K type joint. The mechanical properties of a base material of the high-strength bridge steel K type joint are that Rm is 662-688 MPa, RelReL is 560-611, the ductility is 23-24%, KV2 impact energy is 281-296 J at -40 DEG C, and different-thickness bridge steel is 32 mm+40 mm in thickness; double-sided K type asymmetric grooves are adopted, the groove angle is 50 degrees, and the truncated edge is 2 mm; a WH65Q welding wire and SJ105Q welding flux are adopted for submerged arc welding, the diameter of the welding wire is phi 4.0 mm; WH70Q is adopted for a gas protecting welding wire, and the diameter of the welding wire is phi 1.2 mm; the welding is performed, first gas protecting welding is adopted for bottoming, and then submerged arc welding is performed until a weld joint is filled. The method for hybrid welding of K type joints of different-thickness plates is adopted, so as to solve the problem that the K type joints of different-thickness plates made of large-span high-strenght bridge steel is not preheated prior to weld joint welding and does not undergo heat treatment after the welding, and the KV2 impact energy of the joint reaches 135-223 J at -40 DEG C.