Based on experiences gained in successful development of J-series down-the-hole impactors and bits, and with reference to some strutural features of foreign high pressure impactors, a new JW-150 high pressure down-the-hole impactor was designed with water separated and air chamber inside. In designing, computer simulation, optimization of working parameters, modification of processing and heat-treatment technology are highlighted. Therefore, its main performances indices and penetration rate have reache dthe advanced level of foreign products. Presently, JW-150 high pressure down-the-hole impactors are widely used in many mines and engineering sites in home and abroad, yielding remarkable economic benefits and social efficiency.