The invention relates to a method for producing clean diesel oil by vegetable oil; the mixed raw material of mineral oil and vegetable oil is contacted with hydrogen, under the hydrotreatment reaction condition, hydrogenation reaction is carried out under the action of hydrotreating catalyst, wherein the proportional range of the mineral oil and vegetable oil is calculated by the following formula by weight: the proportion of the mineral oil in the mixed raw material is equal to (0.05-0.3)percent/sulphur content percent in the mineral oil; in the invention, the mixed raw material of mineral oil and vegetable oil is adopted, as the mineral oil is diesel fraction with high sulphur content, but no sulphur is contained in the vegetable oil, the mixed raw material is adopted, so as to meet needs that the hydrogenation catalyst is kept to be in a vulcanizing state, prolong the life of the catalyst, reduce the difficulty of high-sulfur mineral oil desulfuration reaction to the maximum extentand produce ultra low sulfur diesel.