The invention discloses an overline continuous beam whole-span disassembling method which comprises the following steps: S1 of arranging a temporary buttress; S2 of splicing a combined support; S3 of jacking and testing continuous beams; S4 of cutting in a whole-span mode; S5 of transferring beam bodies. The invention further discloses a disassembling combined support in the method. The disassembling combined support comprises a multi-shaft hydraulic flat car, a steel tube buttress set, a jacking system and a distributing beam which are sequentially connected from bottom to top. The method disclosed by the invention has the advantages of quickness, high efficiency, safety, stability, convenience in operation and the like, further reduces construction road occupying time to the maximum extent, has smallest effect on overline traffic and has obvious excellence and advancement in numerous overline continuous beam disassembling methods.