Electric field and magnetic field can be applied to any liquid suspensions with a discrepancy in permittivity or permeability between the suspended contents and the base liquid (Tao et al., 2014, 2016; Du et al., 2011; Tao et al., 2011; Huang et al., 2011). As we know, the diesel has some benefits compared to gasoline (Aoyagi et al., 2006). And the fractional distillate of petroleum fuel oil has the limited reserve. Fortunately, the biodiesel can be used for the petroleum diesel engines directly and with a reduction in greenhouse gas emissions. At the same time, it has a bigger issue of energy security. For these reasons, the scientists of all over the world already started to try biodiesel, but the biggest problem is high viscosity. So it is really important to reduce the viscosity of biodiesel (Hiroshi et al., 2004). We tested the biodiesel sample made in Japan, we reduced the viscosity 25.5% with electric field strength at 1667 V/mm. At the same time, the average droplet size is reduced 41% dramatically, engine combustion will increase 20%.