Abstract: In order to improve the efficiency of short pulse laser drilling,a double-pulse technique is put forward.The double-pulse herein represents two neighboring nanosecond pulses with several tens of nanoseconds interpulse separation,acquired by temporal pulse shaping.In the experiments,laser beams from a Q-switched Nd: YLF laser was focused on steel workpieces 0.4mm~1.0mm thick.The influence of energy density,repetition rate and the ambient gas pressure on ablation rate was studied. Che experimental results show a significant enhancement of ablation rates using double-pulse instead of conventional single-pulse under the same condition of energy density and pulse repetition frequency.The ablation mechanism of the double-pulse drilling,intauding material preheating,melt flow accelerating and quasi-vacuum environment,was discussed respectively.These results are important for practical efficient laser drilling.