The invention discloses synthesis of antibiotic ceftazidime, ceftazidime for injection and a preparation method of ceftazidime. 7-ACA is served as a raw material, silanization and iodo reaction are carried out, and pyridine, hydrochloric acid and water are added to obtain TA (7-PyCA); ceftazidime active ester is added in an organic solvent and an inorganic solvent to obtain new modified ceftazidime active ester; TA is added in new modified ceftazidime active ester, organic mixed solvent and triethylamine are added, then acid water and an acetone solution are added to obtain TC (ceftazidime dihydrochloride), and ceftazidime is obtained through the reaction. The synthesis of ceftazidime provided by the invention has the advantages that ceftazidime is high in yield, operation processes are simplified, production cost is low, ceftazidime is applicable to industrial production, obtained products can be stored for a long time, a structure is stable, and impurity content is low. Ceftazidime for injection has the advantages of being moderate in grain size, good in clarity, less in impurity content, excellent in quality, stable and the like, and is high in split charging efficiency in production, good in content uniformity, high in medicine dissolution rate in clinical application and good in dissolubility.