The invention discloses a great-core-diameter optical fiber coupler, which comprises an input optical fiber and n output optical fibers, wherein the n is greater than or equal to 1 but smaller than or equal to 6, the core diameter of the input optical fiber is 200 to 600mum, the core-to-sheath ratio range of the input optical fiber is 1:1.04 to 1:1.25, the core diameter of each output optical fiber is 200 to 400mum, the core-to-sheath ratio of the output optical fiber is identical to that of the input optical fiber, the input optical fiber and the output optical fibers are fixed and twisted in a coupling region, one end, in the coupling region, of the input optical fiber is the output end of the input optical fiber, the other end of the input optical fiber is the input end of the input optical fiber, one end, in the coupling region, of each output optical fiber is the input end of each output optical fiber, and the other end of each output optical fiber is the output end of the output optical fiber. The great-core-diameter optical fiber coupler has the advantages that the optical fiber coupling difficulty is low, the light splitting ratio of the coupler is uniform, the optical fiber uncoaxiality caused by optical fiber accumulation in the coupling region is reduced, the light spot divergence angle is smaller than 30 degrees, the transmittance is greater than 70 percent, any light splitting ratio can be realized, and the light splitting ratio deviation is +/-7 percent.