The invention discloses an annular permanent magnet assembling mechanism, relates to a mechanical assembling mechanism and aims to solve the problem about eccentricity during reverse assembling of annular permanent magnets. The annular permanent magnet assembling mechanism comprises a regular octagonal threaded sleeve, a regular octagonal through hole sleeve and two groups of locknuts, the regular octagonal threaded sleeve, the regular octagonal through hole sleeve and the locknuts sleeve a central long screw column, four ribs combined with the threaded sleeve and four ribs combined with the through hole sleeve are crossly distributed, and the regular octagonal through hole sleeve is arranged between two groups of locknuts. By the aid of step action of transmission of the central long screw column, repulsion force stressed on permanent magnet combination during reverse assembling is overcome, the permanent magnet combination is kept close, and eccentricity of the permanent magnet combination during reverse assembling is avoided greatly by supporting of the central long screw column, the ribs and metal buttons. The annular permanent magnet assembling mechanism is applicable to assembling of the annular permanent magnets.