NOVELTY - Preparation of alkaline-earth metals glycerin compound catalyst comprises preparing low-carbonate ethanol solution of 0.1-0.4 g/ml of alkaline-earth metal chloride, adding alkaline metal hydroxide and glycerin; heating the reactor; removing the transparent solution to conical flask or other container with sealing device when there is no vapor steamed out; adding the prepared low-carbonate ethanol of alkaline-earth metal chloride into the transparent solution when the transparent solution is cooled at 40-60 degrees C; cooling; collecting precipitate; and sealing to preserve after filtering.    USE - The process is useful for preparing alkaline-earth metals glycerin compound catalyst that is used for catalyzing biodiesel production (all claimed).    ADVANTAGE - The catalyst can accelerate the exchanging reaction between low-carbonate ethanol and fat in a short time; where the exchanging rate is high; and the catalyst can be recycled by centrifuging or filtering; thus, the catalyst can be used repeatedly. Moreover, the catalyst is active; the reaction condition is moderate; and the preparationg technology is simple.    DETAILED DESCRIPTION - Preparation of alkaline-earth metals glycerin compound catalyst comprises preparing low-carbonate ethanol solution of 0.1-0.4 g/ml of alkaline-earth metal chloride, adding alkaline metal hydroxide and glycerin; where every 100 ml glycerin is added with 10-40 g of alkaline hydroxide; heating the reactor at 110-160 degrees C while stirring for 2-6 hours, removing the transparent solution to conical flask or other container with sealing device when there is no vapor steamed out; adding the prepared low-carbonate ethanol of alkaline-earth metal chloride into the transparent solution when the transparent solution is cooled at 40-60 degrees C; where white precipitate is formed in the solution along with drastic heat releasing; cooling at room temperature when there is no precipitate; collecting the precipitate by filtering with Buchner funnel; rinsing the solid with low-carbonate ethanol during filtering process for 2-3 times to remove the redundant glycerin, sealing to preserve after filtering; and obtaining alkaline-earth metal glycerin compound with catalyzing activation.