Abstract: The laser welding system was designed for the sockets and cover of motorrotor. Because of the tolerance of the length and the installing dimensions after the ork-pieces being assembled,the special fixture was designed to absorb the tolerance which consists of the swiched fixture,jacking component,up-stop component and rotary fixture. The work-pieces were fixed in the swiched fixture and jacked upwards the upstop component,which used the upper surface as the position datum,realized the positioning for the work-piece precisely.