A multi-pole circuit breaker with auxiliary supports, comprising a base, N single-pole circuit breaking units, an operating mechanism controlling the single-pole circuit breaking units to perform breaking operations, and a rotation axis assembly for all the single-pole circuit breaking units, each single-pole circuit breaking unit comprising a housing, an extinguishing chamber, two stationary contacts (29, 33) distributed symmetrically, two arc extinguishing grids (36, 37) distributed symmetrically, and two terminal strips connected with the stationary contacts respectively, the rotation axis assembly consisting of N-1 supporting assemblies and N support shaft parts in series, two sides of each supporting assembly being both provided with a support shaft parts, and each support shaft parts being provided with a movable contact bridge, the operating mechanism being directly connected with the rotation axis assembly in order to directly drive N movable contacts on the support shaft parts and the stationary contacts (29, 33) of the single-pole circuit breaking units to perform synchronous opening/closing operation, the multi-pole circuit breaker being characterized in that: the supporting assembly consists of a rotation axis, an auxiliary support, an auxiliary support bearing and at least one supporting rod; a shaft hole is arranged on the support shaft parts, the rotation axis is inserted into the support shaft parts at two sides of the support assembly through the shaft holes, and the rotation axis maintains synchronous revolution with the support shaft parts, a bearing hole is arranged on the auxiliary support, an outer side of the bearing is tightly assembled with the bearing hole of the auxiliary support, and an inner side of the bearing is tightly assembled with the rotation axis, at least one supporting rod installing hole is arranged on the auxiliary support, the at least one supporting rod is tightly assembled with the at least one supporting rod installing hole, the at least one supporting rod is arranged in parallel to the rotation axis, and all the supporting assemblies share the at least one supporting rod, the operating mechanism is fixedly connected with a rotation axis assembly through the at least one supporting rod, the at least one supporting rod is fixedly installed on a housing of each single-pole circuit breaking unit and provides stable supporting force for the rotation axis through the auxiliary supports. the rotation axis assembly consisting of N-1 supporting assemblies and N support shaft parts in series, two sides of each supporting assembly being both provided with a support shaft parts, and each support shaft parts being provided with a movable contact bridge, the operating mechanism being directly connected with the rotation axis assembly in order to directly drive N movable contacts on the support shaft parts and the stationary contacts (29, 33) of the single-pole circuit breaking units to perform synchronous opening/closing operation, the multi-pole circuit breaker being characterized in that: the supporting assembly consists of a rotation axis, an auxiliary support, an auxiliary support bearing and at least one supporting rod; a shaft hole is arranged on the support shaft parts, the rotation axis is inserted into the support shaft parts at two sides of the support assembly through the shaft holes, and the rotation axis maintains synchronous revolution with the support shaft parts, a bearing hole is arranged on the auxiliary support, an outer side of the bearing is tightly assembled with the bearing hole of the auxiliary support, and an inner side of the bearing is tightly assembled with the rotation axis, at least one supporting rod installing hole is arranged on the auxiliary support, the at least one supporting rod is tightly assembled with the at least one supporting rod installing hole, the at least one supporting rod is arranged in parallel to the rotation axis, and all the supporting assemblies share the at least one supporting rod, the operating mechanism is fixedly connected with a rotation axis assembly through the at least one supporting rod, the at least one supporting rod is fixedly installed on a housing of each single-pole circuit breaking unit and provides stable supporting force for the rotation axis through the auxiliary supports. the supporting assembly consists of a rotation axis, an auxiliary support, an auxiliary support bearing and at least one supporting rod; a shaft hole is arranged on the support shaft parts, the rotation axis is inserted into the support shaft parts at two sides of the support assembly through the shaft holes, and the rotation axis maintains synchronous revolution with the support shaft parts, a bearing hole is arranged on the auxiliary support, an outer side of the bearing is tightly assembled with the bearing hole of the auxiliary support, and an inner side of the bearing is tightly assembled with the rotation axis, at least one supporting rod installing hole is arranged on the auxiliary support, the at least one supporting rod is tightly assembled with the at least one supporting rod installing hole, the at least one supporting rod is arranged in parallel to the rotation axis, and all the supporting assemblies share the at least one supporting rod, the operating mechanism is fixedly connected with a rotation axis assembly through the at least one supporting rod, the at least one supporting rod is fixedly installed on a housing of each single-pole circuit breaking unit and provides stable supporting force for the rotation axis through the auxiliary supports.