Improvement of atomization process is one of the most effective methods to promote the cold-start period of an internal combustion engine (ICE) using port fuel injector (PFI). In this paper authors present a fuel heating method using microwave energy through the local-contact microwave-heating injector (LMI) to enhance the properties of fuel sprays in such a risky working area of ICE. Temperature and mixing ratios of blended fuel are varied and characteristics of atomization are investigated. The fuel using in experiments is blended fuel of gasoline and ethanol, the mixing ratio is varied among 0 (E0), 5 (E5), 50 (E50), and 100 (E100) percentages in volume ratio of ethanol. The temperature of the fuel is measured just before the injection by using K-typed sheath thermo-couple. Spray characteristics measured are Sauter Mean Diameter (SMD), droplet size distribution, spray cone angle, and particle size distribution width. The SMD and the droplet size distribution are measured by using laser diffraction method. The spray cone angle is measured through pictures of actual appearance atomization. The results show that, the higher percentage of ethanol in the blended fuel the higher temperature the fuel can reach, except the case mixing ratio of 0% ethanol, in which fuel temperature still remain no matter how is the heating duration. At each blended amount of ethanol, except E0, all of the spray atomization measured and analyzed characteristics show the clear improvements with the increase of fuel temperature.