In the manufacturing process of all-fiber Mach-Zehnder interferometer, it needs to cut, weld and taper the photonic crystal fiber and single-mode fiber. First, by using the theory of contact mechanics, the internal stress of the photonic crystal fiber in the V-groove was analyzed, and the maximum stress point inside the photonic crystal fiber was deduced at the outermost air hole parallel to the contact surface. In conclusion, the stress distribution diagram and strain distribution diagram of the photonic crystal fiber were given, and the maximum load when the photonic crystal fiber is cut, fused and fixed was calculated. Then, the stress analysis of the fiber with air ball inside was carried out, and the maximum stress point inside the fiber was deduced from the edge of the air ball closest to the surface of the fiber. Finite element analysis was used to verify this conclusion, and the internal tension and stress distribution diagrams were given, providing a theoretical basis for the taper of the air ball in the optical fiber to the spindle shape.