Abstract: Plasma-activated water (PAW) has a broad application prospect in the fields of medicine, food industry, and agriculture. In this paper, a coaxial needle-cylinder electrode, driven by high-frequency AC high voltage, was used to generate air plasma jet to prepare PAW. The shape, electrical and optical characteristics of air plasma jet under various electrode arrangements and air flows, the physical and chemical properties and inactivation efficacy of PAW were investigated. The results show that, when the air flow is lower than 5 L/min, which means laminar flow, the jet length and discharge power will increase with the air flow. When the air flow is higher than 5 L/min, changing to turbulent flow, the jet length and discharge power will decrease. Besides, the power will decrease slightly when contacting the liquid surface. Optical emission spectrum shows that the vibration temperature of air plasma jet is higher than other discharge patterns. Activation of deionized water can reduce its pH value and increase its oxidation reduction potential and electrical conductivity. PAW shows better inactivation efficacy on bacteria with the increase of activation time and reduces over 90% microorganism from infected grape leaves, whereas, its inactivation ability decreases significantly after placing at room temperature for one hour. This study provides a reference for the field application of air plasma jet and PAW.