Abstract: By-product of alkali-refining of edible oils, which can cause environmental pollution and waste of resource, is always discarded during the process of production of edible oils. In order to solve the problem, experimental study was conducted to analyze the preparation of biodiesel from by-product of alkali-refining of edible oils. The way and technologic flow of circulating gas phase esterification-water vapour distillation were improved to explore the solution of removing water continuously and reacting quickly in esterification. Optimal technological parameters were obtained. The experimental setup includes the reactor of gas-phase esterification, gasifying device of methanol, refining device of raw product and the segregator of oil and water. The experimental results show that the conversion rate of preparation biodiesel from by-product of alkali-refining of edible oils exceeds 99% by following conditions: esterification temperature at (100±5)℃, sulfuric acid(0.5～0.8% w/w) or p-toluensulfonic acid(3～4% w/w) as catalyst, gaseous methanol dosage of 6L/min, reaction time between 90～120 min, liquid phase between 160～220℃ and gas phase between 120～190℃ in refining device, temperature of water vapour at (100±5)℃ and gaseous dosage of 5 L/min. The main quality indexes of biodiesel from by-product of alkali-refining of edible oils are basically up to par of American ASTM standard of bioeiesel and it is similar to 0# diesel oil.