The invention discloses a 2450-MHz high-power continuous-wave magnetron and a preparation method thereof. The 2450-MHz high-power continuous-wave magnetron comprises an anode cavity combination unit (1), a cathode outgoing line combination unit (2), an output window combination unit (3) connected with the anode cavity combination unit (1), and an output antenna (4) fixed at the anode cavity combination unit (1); the other end of the output antenna (4) is arranged inside the output window combination unit (3); and the anode cavity combination unit (1) is connected with a cavity cooling water inlet-outlet pipe (5). The structure of the provided continuous-wave magnetron is designed reasonably; the power of the magnetron is high and the output power can reach over 30 KW; the service life can reach more than 5000 hours; the microwave leakage is less; and the security performance is high. Besides, according to the preparation method of the continuous-wave magnetron, lots of experiment screening is carried out; and the method has the advantages of reasonable process design and high operability. Moreover, the prepared magnetron with characteristics of high gas tightness, a high vacuum degree, low sparking probability and stable performance enables various defects existing in the prior art to be overcome.