The study was done to investigate the prescription, determination and preparation process of ramosetron injection.Mannitol, sorbitol and dextran were used as filling agents in the ramosetron injection preparation and their content and related substances were determined by HPLC.Composition of mannitol 100 g and ramosetron 0.3 g was determined as the best prescription at last.The sample amount of three batches were 100.5%, 101.2%, 99.6%, and related substances were 0.17%, 0.17%, 0.18%, resp., meeting the requirements of new drugs.The prescription and preparation process of the ramosetron injection is feasible and controllable.