A reaction kinetics study was performed for all cis-polyaniline nanotube (ACPN) film modified electrode for fast ascorbic acid detecting. An ACPN film modified electrode exhibited excellent electrocatalytic activity, a low detection limit and a high sensitivity to ascorbic acid (AA). It is found that AA can be electro-catalytically oxidized on an ACPN film even at a concentration less than 1 mM. A mechanism of AA electrooxidation on the ACPN film modified electrode was proposed. Furthermore, the detection sensitivity was regulated by tuning the film thickness, and the optimized fabrication conditions for the ACPN film modified electrode was obtained. Based on the reaction kinetics study, the catalytic rate constant for the best electrode was found to be 6.3x10(6) cm(3).mol(-1).s(-1). It is expected that such a sensor based on the ACPN film can be widely applied for AA detection.