NOVELTY - alpha -ketophenylalanine calcium is prepared by mixing 100-150 pts. wt. hydantoin, 15-30 pts. wt. strong alkali, and 300-800 pts. wt. water, adding 100-150 pts. wt. benzaldehyde, reacting at 80-90 degrees C for 4-9 hours, cooling to 25-35 degrees C to obtain white solid isobutyl hydantoin, adding 400-600 pts. wt. 40-60 wt.% aqueous strong base dropwise at 20-30 degrees C, heating and stirring to reflux for 2-5 hours, cooling to room temperature, adjusting pH to less than or equal to 0.5 with strong acid, extracting with ether or ester solvent, combining organic phase, adding 30-80 pts. wt. organic base to organic phase, and mixing.    USE - Preparation of alpha -ketophenylalanine calcium (claimed).    ADVANTAGE - Preparation of alpha -ketophenylalanine calcium is simple, low-cost, has high reaction yield, mild reaction conditions, easy operation, and readily available raw materials, improves equipment utilization, avoids alpha -ketophenylalanine decomposition, produces less waste and environmental pollution, and does not require repeated recrystallization, and alpha -ketophenylalanine is stable and has high purity.    DETAILED DESCRIPTION - alpha -ketophenylalanine calcium is prepared by mixing 100-150 pts. wt. hydantoin, 15-30 pts. wt. strong alkali, and 300-800 pts. wt. water, adding 100-150 pts. wt. benzaldehyde, reacting at 80-90 degrees C for 4-9 hours, cooling to 25-35 degrees C to obtain white solid isobutyl hydantoin, adding 400-600 pts. wt. 40-60 wt.% aqueous strong base dropwise at 20-30 degrees C, heating and stirring to reflux for 2-5 hours, cooling to room temperature, adjusting pH to less than or equal to 0.5 with strong acid, extracting with ether or ester solvent, combining organic phase, adding 30-80 pts. wt. organic base to organic phase, mixing, adding 80-100 pts. wt. water, extracting combined aqueous phase, adding 100-550 pts. wt. alcohol to aqueous phase, adding 60-90 pts. wt. 20-30 mass% aqueous calcium chloride solution dropwise, incubating at 25-30 degrees C for 2 hours, filtering, washing, and drying.