Through a theoretical analysis of fiber coupling conditions, an optical system of an beam-expanded optical fiber connector is designed and simulated in the hybrid mode of ZEMAX software. Quantitative analysis of the changes in beam quality and coupling efficiency caused by alignment errors of the collimator lens and focusing lens are performed. Simulation results show that the collimator lens and the focusing lens have eccentricity or tilt errors that are within the allowable range. The positions of the two lenses can be adjusted to compensate for aberrations and optical axis shifts to ensure that the beam quality and coupling efficiency meet standards. The simulation results are experimentally verified. Then, the allowable range of the alignment error of the optical fiber connector at different diameters is simulated and an alignment error compensation formula is derived. During the design and adjustment of the beam-expanded fiber optic connector, and derive the alignment error compensation formula. The alignment error causes by the misalignment of the collimator lens can be compensated by the focusing lens, which increases the design accuracy and simplifies the adjustment process. Finally, according to the results of the alignment error analysis, we design and manufacture a 12 kW@600 μm beam-expanded optical fiber connector.