NOVELTY - The method involves performing a hydrotreating step for treating a load e.g. oil of plant origin, in the presence of hydrogen in a three-phase hydro-treating reactor (15). The hydrotreated effluent is separated so as to produce a gas fraction (19), liquid fraction (28) including paraffin, and a fraction including solid impurities such as alkaline metals. The hydrogen is mixed with the load such that hydrogen-load ratio lies between 70 and 1000 Nm3/m3 of load. The output effluent is separated into one gaseous fraction and a middle distillate fraction.    USE - Method for conversion of a load output i.e. rough or semi-refined loads such as oils and fats of plant or animal origin (all claimed) such as rapeseed oils, and oils of jatropha, soya, palm, sunflower, olive, copra, camelina, fish oils or heterotrophic or autotrophic oils, algae oil, beef tallow, loads containing triglycerides and/or free fatty acids and/or esters, from renewable sources so as to produce middle distillates utilized as a base for a fuel such as petrol, diesel, kerosene and marine fuel. Can also be used for residues output from paper industry such as tall oil.    ADVANTAGE - The hydrogen is mixed with the load such that hydrogen-load ratio lies between 70 and 1000 Nm3/m3 of load, and the output effluent is separated into one gaseous fraction and one middle distillate fraction, thus allowing to produce middle distillates with improved output and quality. The method avoids or decreases the need for gas or liquid hardenings. The method eliminates solids at the end of hydro-treating step in bubbling bed, thus increasing duration of cycle of a section of a fixed-hydroisomerization bed and performing hydroisomerization without risk of premature blockages.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic illustration of separation of a liquid effluent output from a hydro-treating step with paraffin allowing partial elimination of water contained in the effluent.    Three-phase hydro-treating reactor (15)    Gas fraction (19)    Liquid fraction (28)    Kerosene fraction (46)    Pipe (48)