a technological method for synthesizing optically pure l -/ d - lactide by using a biogenic guanidine catalysis method . the method of the present invention comprises : by using biogenic guanidine creatinine as a catalyst and l -/ d - lactic acid as a raw material , synthesizing optically pure l -/ d - lactide by using a reactive reduced pressure distillation catalysis method . the method of the present invention has advantages that the used catalyst is biogenic guanidine creatinine and free of toxicity , metal , and cytotoxicity ; the synthesized lactide is high in optical purity 25d =− 276 ˜− 280 , and the specific rotation of the d - lactide 25d = 280 ), and does not contain any metal ; the amount of the catalyst used in reaction is low , the technological process is simplified ; and the technological method is simple and convenient to operate and easy in industrial implementation .