The invention relates to a three-channel broadband coaxial rotary hinge and an implementation method thereof, and mainly solves the problems of transmission and coupling conversion of signals of a rotary end and a fixed end of a first channel and three-channel integration. According to the three-channel broadband coaxial rotary hinge, a first channel rotation transition radio frequency socket anda rotation end coaxial line are electrically connected through a first transition reed, a fixed end radio frequency socket and a fixed end coaxial line are electrically connected through a second transition reed, a second channel dielectric sleeve is clamped on a first channel fixed end coaxial line outer conductor, and a transmission ring is embedded in a dielectric sleeve, so that a first channel cavity and a second channel cavity are small in space size, high in rotary hinge working frequency and wide in bandwidth; and two radio-frequency cables penetrating through a third channel bush anda rotary transition step shaft are connected with the first channel rotary transition radio-frequency socket and the second channel rotary transition radio-frequency socket respectively, the bush is embedded with the rotary transition step shaft, the first channel and the second channel are integrated in a radial overlapping mode, the third channel, the first channel and the second channel are integrated in an axial stacking mode, and the three channels are independent of one another in structure and are integrated in a modular mode.