A novel system combining acoustic wave impedance (AWI) analyzer with UV-vis spectrophotometer was developed for the study of chromium (VI) reduction kinetics by Pseudomonas aeruginosa. AWI gave information about the growth of Pseudomonas aeruginosa, and UV-vis spectrophotometer gave information about the concentration of chromium (VI) simultaneously. A combined system response model, for chromium (VI) reduction kinetics at lower initial chromium (VI) concentrations, was derived and proved based on the novel system. Taking into account the effect of bacterial growth on chromium (VI) reduction, the new model successfully simulated chromium (VI) bioremediation process. By fitting chromium (VI) reduction data toward the derived model, the kinetic parameters related to the process were obtained. When the concentration of peptone was 10 g L-1, the half-velocity reduction rate constant K (C) and the maximum specific chromium (VI) reduction rate constant nu(max) were 0.7682 mg chromium (VI) L-1 and 2.5814 x 10(-12) mg chromium (VI) cells(-1) h(-1), respectively. It was found that the combined system can provide real-time, reliable, and two-dimensional kinetic information, and can be applied to study other biological processes.