A highly sensitive linear sweep voltammetric method was developed for the determination of paclitaxel and the mechanism of the binding of paclitaxel to tubulin was studied. Tubulin dimer formed with paclitaxel an electrochemically nonactive complex with a combination ratio of 2:2. Its stability constant was 2.85×1022. So the tubulin dimer had two binding sites for paclitaxel. The experiment showed that the binding sites of paclitaxel to tubulin dimer were different from that of Ca2+ to tubulin dimer.