In order to study the coupling mechanism of butterfly optical communication lasers, a chip-lens-single mode fiber simulation model was established. Based on the coupling theory, the concept of tolerance was introduced, and the effect of space position error on coupling efficiency was analyzed. By comparing the tolerance that the lens and the fiber in each direction, combined with the offset phenomenon after welding, the packaging sequence that the lens first and then the fiber was proposed, and an experimental platform was built for verification. The results show that in the comparison experiment, the maximum power obtained by lens priority package is 1800μW, while the maximum power obtained by fiber priority package is only 1200μW. The effect of the offset after welding is better when the lens is encapsulated first. This research provides a reliable reference for the actual packaging and production of butterfly devices.