The heat dispersion of a cooler which we made was theoretically simulated and the thermal conductivity of the packaging material was analyzed. It was proved the diode laser could operate in high power density and high duty cycle. The key technique for high density packaging was improved. The thickness of the gilded heat sink was 3~5 mm, and that of the solder was 4~7 mm. The thermal resistance of the packaged LD bar was 0.115 ℃/W. The output power of the diode laser arrays was 986 W when the current was 100 A and the duty cycle 15%. The slope efficiency of each bar was 1.25 W/A and the current threshold was about 20 A. The peak power density could be as high as 1.5 kW/cm2 when the duty-cycle was 15%.