The invention discloses a method for preparing candle base oil by using vegetable oil. The method comprises the following steps: i) carrying out fractionation and/or hydrotreating on the vegetable oil; ii) adding a decolorising agent to the vegetable oil processed in the step i), and carrying out vacuum decoloring treatment; iii) carrying out deodorization treatment on the decolorized vegetable oil obtained in the step ii), so as to obtain the candle base oil. The vegetable oil is adopted to carry out fractionation and/or hydrotreating, and then decoloring and deodorization treatment is carried out to obtain palm stearin, hydrogenated palm oil, hydrogenated palm kernel oil and hydrogenated soybean oil with different application performances as the candle base oil. Whole vegetable oil materials are provided for candle production enterprises to produce different candles, the production cost and the export cost are reduced, and the method is environmentally friendly.