Aiming at the precise coupling problem of the optical fiber collimating lens signal, one of the core components of the optical fiber joint, a single-mode large beam optical fiber connector is designed using a doublet lens. By analyzing the characteristics of dual lens, the coupling mechanism of the multi-optical devices in the fiber collimator array, and the transmission loss caused by the three coupling deviations between the collimating lenses, the transmission loss formula of the coupling system is derive. Based on MATLAB analysis, the angular mismatch has the greatest effect on the coupling loss of the collimator, and the axial mismatch has the least effect. The optical simulation software ZEMAX is used to simulate the joint in sequence and hybrid modes, and Origin is used to plot the signal coupling efficiency curves under different mismatch conditions. The results show that when the core diameter of single-mode fiber is 12 μm, the coupling efficiency reaches 92.42%. Finally, an experimental system is built through the optical platform to verify the accuracy of the simulation results.