·OH plays a crucial role in many fields,having aroused wide public concern in the world.Atmospheric Pressure Plasma Jet,which can be achieved by portable device due to working without the vacuum environment,has the advantages of high concentration of reactive species,high electron temperature and low gas temperature.It has become an important research topic in the field of gas discharge with a strong prospect.Especially,how to induce plasma jet to produce ·OH has become a new hotpot in the field of low-temperature plasma.It has been reported that mass ·OH can be induced successfully when water vapor is added to the working gas,but it will be unstable when the concentrate of water reaches a certain degree.Thus,a device of argon plasma jet with a Ring-to-Ring Electrode Configuration has been designed to interact with water in the surrounding air to generate ·OH under atmospheric pressure.In order to increase the production of ·OH,ultrasonic atomizing device is introduced to promote water concentration around the plasma plume.The generating rule of OH(A2Σ+) induced by water has been extensively studied under different voltages and flow rate.·OH output induced by the plasma has been tested by emission spectrometry,and at the meanwhile,Ar atomic spectral lines at 810.41 and 811.48 nm are also recorded in order to calculate the electron temperature in argon plasma plume.The results show that the water surrounding the plasma plume can be induced to produce ·OH,and OH(A2Σ+) output increases with the electrode voltage rising from 20 to 28 kV.When the flow rate increases from 100 to 200 L·h-1,the OH(A2Σ+) output increases,but from 200 to 600 L·h-1,it decreases.The production rules of OH(A2Σ+) is the same as that of electron temperature.Therefore,the presumption is proved that ·OH output mainly affected by electron temperature.