The invention relates to the technical field of an optical fiber detection device, in particular to a multichannel long optical path air chamber applied to the inside of SF6 equipment. The multichannel long optical path air chamber comprises a casing and an optical detection device, wherein an annular fixing disc is arranged in the casing; the optical detection device comprises N laser transceivers; the N is an integer being greater than 2; the N laser transceivers are annularly arranged on the fixing disc at intervals; and the N laser transceivers are sequentially in end-to-end connection through an optical fiber. The multichannel long optical path air chamber has the advantages that the structure is reasonable; the optical fiber is connected in from a guide-in hole; the laser enters an excitation collimator through the optical fiber; the laser is converted into parallel light by the excitation collimator, and the parallel light is received by a receiving collimator arranged in the opposite side; the receiving excitation collimator receives optical signals and transmits the optical signals onto an adjacent excitation collimator through the optical fiber; after the roundtripping for many times, the optical signals are guided out through the optical fiber on a guide-out hole; the detection optical path is changed into the integral multiples of the diameter of the fixing disc; the detection optical path and the detection precision are greatly improved; and the fixing disc can be carried on a flange with any diameter, and can be applied to equipment of any specifications.