Abstract: A manufacturing method of a high-reliability optical fiber coupler includes (1) manufacturing the optical fiber coupler by a fused biconical tapering process employing a parallel sintering process, and detecting via a tension test the strength of the optical fiber resulting from the sintering process, securing the strength thereof being greater than or equal to 1N; (2) fixing both ends of the sintered optical fiber coupler in a U-shaped quartz groove via hardening adhesive, and filling inside of the U-shaped quartz groove around the coupling arm at both ends thereof with adhesive to shorten the suspending length of the optical fiber; (3) inserting the U-shaped groove containing the optical fiber coupler into a circular quartz tube, and fixing both ends of the circular quartz tube via hardening adhesive; and (4) sleeving a stainless steel tube around the circular quartz tube, and sealing both ends of the stainless steel tube.