Abstract: As poly-arginine (Arg6) solution was added to a solution of 1.0×10-5mol·L-1 conjugated poly-electrolyte (CPE) up to the concentration of 15 mg·L-1, the fluorescence of CPE was quenched to an extent of 90% at the equilibrium of the reaction between CPE and Arg6. Various concentrations of trypsin (TPS) solution was added, and finally attained to an extent of 80% when 1 mg·L-1 of TPS was added. Based on these facts, a real-time and non-labelling determination of TPS with its detection limit (3S/N) of 0.1 mg·L-1 was proposed. In the above reactions system, 1 mg·L-1 TPS was fixed, and various concentrations of TPS inhibitor (TPSI) was added, the fluorescence recovery was retarded, and the magnitude of retardation was related with the amount of TPSI added, hence this phenomenon was utilised as a method for determination of TPSI.