The invention belongs to the technical field of bearing test and provides an auxiliary supporting structure of an outer cycle rotating high speed heavy-load support. An annular roller (6), namely an auxiliary support, is arranged below an annular test bearing seat; an auxiliary supporting bearing (5) is mounted in the roller; the roller (6), which forms the auxiliary support, and the test bearing seat (1) have reverse rotation directions; after a test bearing is born, the test bearing seat (1) is in contact with a supporting roller and simultaneously rotates together with the supporting roller; and the load generated by loading is mutually born by a slave test bearing (3) and the auxiliary supporting bearing (5). According to the invention, the bearing pressure of the slave test bearing is effectively eased, the service life of the slave test bearing is prolonged and the difficulties in realizing outer cycle rotating heavy-load bearing tests and selecting corresponding slave test bearings are solved.