Abstract:A new coup ling method between laser diode and multi-mode op tical fiber is presented. The output light from laser diode is collimated using a section of optical fiberwith the diameter of 600μm instead of cylinder lens, and a sphere-end lens fiber rep laces the coup ling partwith focus lens coupling the light to the fiber. Results show that the coupling efficiency is about 80. 0% , at the same time the difficulties of debugging and encap sulation in coup ling system is greatly reduced, composed with cylinder lens and focus lens. And the process is stable. So this coup ling system will be widely used in the future.