Based on linear coupled wave equations,the fused biconical tapered 3×1 fiber coupler with a triangular distribution is discoursed by the method of scattering matrix.The end face effect of optic fiber with circular spherical focused end face is analysed with ray theory.Through cutting off the unpackaged 3×3 fused tapering optical fiber coupler in the waist,and melting the end of its tapered end face into the circular spherical focused end face,optical fiber transmission and fiber coupling,as well as fiber beam splitting can be realized for the special transmission and coupling characteristic in the tapered area and optic fiber with circular spherical focused end face.Results show that the coupling efficiency improve about 70%,and the tolerant disturbance of the coupling system is largely increased.At the same time,the difficulties of debugging and encapsulation is greatly reduced.Therefore this coupler will have widely practical applications.