By using an atmospheric pressure microplasma jet array device driven by a.c. voltage with repetition rate of several kilohertz, we were able to inactivate the resistant Pseudomonas sp HB1 cells in aqueous solution. Measurements showed that all Pseudomonas sp. cells in a suspension of 80 mL with the concentration of similar to 10(8) CFU (Colony-Forming Units) were killed within a treatment time of 6 min. Rather than O radicals, OH radicals or charged species were supposed to play the most important role in the plasma inactivation process by this method. This design can provide an effective mode of killing the resistant microorganism in water.