To determine the dynamic release of tinidazole from the degradable poly-lactic acid (PLLA)-tinidazole blend gel (a periodontal local drug delivery) by high-performance liquid chromatography (HPLC) in vitro and to observe the polylactic acid (as a vector of tinidazole) how to affect the release of tinidazole.HPLC analysis was conducted. The operating conditions were C18-ODS-A column, water-methanol-acetic acid as mobile phase at a flow rate of 1.5 ml/min and a detection wavelength at 310 nm and a column temperature at 30 degrees C.The retention time of tinidazole was about 12 min. There was good linear relationship between the concentrations of tinidazole in blend gel and their peak areas in the ranges of 5 - 500 mg/L. The regression reaction was y = 0.836 + 8.452 2 x 10(-5) x (r = 0.998 6). RSD was 0.2%. Polylactic acid had no influence on the determination of tinidazole. The daily average release of tinidazole was 5.60%. The cumulative release of tinidazole was about 78.40% in 14 days.The in vitro drug release analysis is an useful method in evaluating the performance of local drug delivery system. HPLC analysis is a simple and accurate method with good reproducibility.