The spray characteristics were investigated for the Diesel-methanol-water (DMW) emulsion and commercial Diesel fuel. Droplet diameters and droplet size distributions were measured by Malvern particle size analyzer and spray tip penetration, and cone angles were acquired using the high-speed CCD digital camera. All experiments were conducted by employing a high-pressure fuel injection system under room temperature and pressure. The viscosity property of the experimental liquid was measured by the rotary viscometer to ensure the influence of the liquid physical property on spray characteristics. The changes of the emulsion physical properties, including the dispersed phase content and the emulsifier, caused significant changes of the spray characteristics. It was found that the curve of droplet size distribution of DMW emulsion and Diesel first increased then decreased with the increase of the nominal diameter, but the distribution range of Diesel was narrower than that of DMW emulsion. Furthermore, Sauter mean diameter and other representative drop diameters decreased with the increase of injection pressure, and a higher injection pressure produced finer spray droplets and better distribution uniformity. Under the same conditions, the spray tip penetration and cone angle of DMW emulsion were smaller than that of Diesel, and they decreased with the increase of the dispersed phase content. Meanwhile, a higher viscosity and lower HLB of the emulsifier had a larger atomized particle size and a smaller spray tip penetration and spray cone angle. However, the variation of spray characteristics of different fuels became smaller with increasing injection pressure.