A RP - HPLC method for the determination of cefotiam hydrochloride for injection was established. The HPLC conditions were that using COSMOSIL column（5μm, 250 mm× 4.6 mm）, phosphate buffer and acetonitrile as mobile phase which ration was 88∶12,the flow rate was 1.5 mL/mim,the detection wavelength was 254 nm．The results showed that the calibration curve was linear from 195.8 to 783.3μg/mL the regression coefficient was 0.999 9 and the average recovery of the method was 99.27%, RSD was 0.16 % （n = 9 ）.