Abstract: The semiconductor lasers are widely used in various fields, this requires that their output power is increasingly improved, so the development of high power semiconductor laser with multichip-packaging is one of mainstream. A typical hundred-watt semiconductor laser packaged with 12 chips in ladder form was analyzed in thermal steady-state, obtaining the rule curves of the temperature of active region of chip and temperature rise by thermal coupling in different parameters of heat sink, and a heat sink structure with better heat dissipation was put forward.