Disclosed herein are a process or method for the preparation of prasugrel and several novel crystalline forms of prasugrel hydrochloride. The process comprises preparation of prasugrel by acetylation in solvents which have low boiling point and/or low toxicity, and the process not only avoids using solvents which have high boiling point and/or high toxicity such as toluene, acetonitrile and so on, but also resolves the problem about thermal instability of prasugrel, and the loss of prasugrel is reduced, as well as the yield is raised. The yield of prasugrel is higher than 85% and the purity is higher than 99.5%. The process can prepare prasugrel and its pharmaceutically acceptable salts. The novel crystalline forms of prasugrel hydrochloride are crystalline form H1, H2 and H3, and their performance in oral absorbability, activating metabolism and inhibiting platelet aggregation is excellent. They have a low toxicity and good thermal stability, and are applicable to the preparation of a drug for preventing or treating diseases caused by thrombosis or embolism.