NOVELTY - Solid base catalyst, prepared by putting the active component and the carrier into a mortar, grinding for 1-2 hours under room temperature, sintering for 5-10 hours in muffle furnace at 300-1000 degrees C, and obtaining the finished product, is new. The active component is alkali metal oxide, fluoride, carbonate or nitrate; the carrier is alumina, calcium oxide, magnesia, zinc oxide, zirconia, active carbon, molecular sieve, diatomite, carclazyte, silica gel or pseudo-boehmite; where the active component quality takes 10-120% of the carrier quality.    USE - The solid base catalyst is useful for biodiesel synthesis (claimed).    ADVANTAGE - The solid base catalyst has high production ratio; it is economical, the usage of catalyst is small; the reaction condition is moderate, the reaction time is short; can be used repeatedly; it has no environment pollution; and demand for raw materials is low.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for the synthesis of the biodiesel, using the solid base catalyst and ester exchange, comprising adding oil, lower alcohol and solid base catalyst into three-neck container equipped with electromagnetic stirring, temperature meter and backflow condensing pipe to heat, flowing back and stirring for 1-3 hours; controlling the heat temperature between 50-110 degrees C; filtering the materials, and filtering out catalyst and filtrate, separating the filtrate, filtrating the lower layer of glycerin, adding sodium hydrogen carbonate (NaHCO3) solution with 5-10% mass fraction into the upper layer of mixture, the adding amount is 2-6 times of the upper mixture quality, washing it till neutralizing performance, removing the unreacted free fatty acid, separating upper layer of organic phase with tap funnel, drying the organic phase with anhydrous magnesium sulfate (MgSO4), removing the drying agent through filtering, depressurizing and distilling, and obtaining the light yellowish transparent product, which is biodiesel.