The core diameter of the single-mode fiber is about 0.006mm to 0.009mm. Any slight misalignment or deformation of the optical mechanism will cause signification optical losses during connections. Previous studies often concentrated on improving the manufacturing process to obtain high precision components. Although the precision can be controlled, misalignment may still occur due to the contact stress on the connecting interface. This study uses the finite element method to simulate the contact status, and takes the MT series connectors for examples. The MT series connectors use the guide-pin structure to align the both contact surface, and use the spring or clip to keep tight contact. Because the MT ferrules are made of plastic materials, they are softer than ceramic ones and the deformation strains are more significant. For the finite element analysis, the solid model of the MT ferrule can be constructed according to the fiber protrusion, oblique angle, physical contact (PC) radius, and JIS C5981 standard. Using the ANSYS software, simulation result showed that, the fiber center displacement would be 0.9μm for the usually used oblique PC connectors. It will significantly affect the eccentricity values for the single-mode applications because only 1.5μm can be accepted. Using this new standard (eccentricity < 0.6μm) to select ferrules, and making them into connectors, it is found that the insertion losses of 98% connectors are less than 0.3 dB. This result satisfies the requirement for single-mode applications.