The invention disclose the pharmaceutically acceptable salts of optically active quinolone compound useful against infection, specifically disclose the pharmaceutically acceptable salts of (S)-6-fluoro-o-1-methyl-4-oxo-7-(1-piperazinyl)-1H,4 H -[1,3]thiazeto[3,2-a]quinoline-3-carboxylic acid. The pharmaceutically acceptable salts of the present invention are stable and have improved water solubility. They possess higher biological activity, less toxicity for kidney and no stimulus skin and muscle.