Electrospray occurs in various kind of electro hydrodynamic modes that is related to changing flow rate, electric field potential and physical properties of fluid. Therefore, using nanoparticles can control electro hydrodynamic (EHD) modes by means of changing physical properties of fluid. In this study, water based SiO 2 nanofluids with different concentration and flow rate were investigated. The high-speed camera was used to visualize droplets with shadow imaging technique. Electro hydrodynamic transition in both of the dripping and jet regime due to effective parameters in electrospray process was reported. Also, in dripping regime, droplets size was calculated with a Riemann sum by MATLAB image processing. In all of the SiO 2 nanofluids concentration, oscillating micro dripping mode will exist, if Weber number is more than 1.8. In addition, spindle mode appeared before micro dripping mode when electrical Capillary number increased. Otherwise, in dripping regime with high Capillary number, going up to 50 percent in flow rate, can preserve droplets size in a constant magnitude, approximately. However, for any nanofluids concentration in dripping regime with a specified flow rate, rising Capillary number has a similar effect. Adding nanoparticles in deionized water not only can remove jet regime in laminar water based SiO 2 iissated nanofluids, but also can make electro hydrodynamic modes mono-regime. Keywords: Electrospray, Controlling Electro hydrodynamic, Nanofluids, SiO 2 , High speed camera, Shadow imaging technique