The present invention relates to a process for preparing fuel-in-water emulsions from oil refining residues, in both continuously or in batches, by adding an emulsifying agent to disperse the residual oil in water and facilitate its transportation. This process does not require the use of chemical substances like stabilizers or diluents for its preparation. The vacuum residue is not limited to specific characteristics and the water used, can be distilled, tap water or saltwater (seawater). The process requires low concentration of a non-ionic surfactant; and the emulsions obtained have proportions from 70 to 90% by weight of refining residues, 10 to 30% by weight of water and from 0.1 to 1% by weight of surfactant.The fuel-in-water emulsion is produced from oil refining residues, such as residues of atmospheric and vacuum distillation, heavy fuel oils and similar, and it is formed from 70 to 90% by weight of refining residues, 10 to 30% by weight of water and from 0.1 to 1% by weight of non-ionic surfactant. This fuel is efficient to its burned, because the fuel oil droplets have the best size to be completely burned into the flame, which has a favorable effect to reduce the unburned particle emissions. In addition, the emulsified fuel remains stable for an enough period for its storage and subsequent injection to the combustion equipment.