Flat-fan air inclusion nozzles, usually with a high-pressure range of 1-1.5 MPa, have been widely used as one of the best drift control methods on agricultural boom sprayers in Japan. To get a better understanding of the relationship between the nozzle design parameters (pre-orifice diameter and final orifice area) and the initial spray characteristics (droplet size characteristics, spray angle, liquid flow rate, and included air within droplets), the influence of the above parameters of the KIRINASHI ES series nozzles on the initial spray characteristics was investigated under different nozzle pressures. The results show that the pre-orifice diameter, final orifice area, and nozzle pressure significantly affect the volume median diameter (D-v0.5). In addition, the nozzle pressure and the pre-orifice diameter had positive correlations with the spray angle while the pre-orifice diameter and the final orifice area significantly influenced the spray liquid density which can indicate the quantity of included air within droplets. The corresponding multivariate regression analysis was carried out and relatively high values of the coefficient of determinations (R-2) were obtained between several nozzle parameters and the D-v0.5, and also the spray liquid density and the liquid flow rate.