Abstract: In order to study the rapid process of transfer and reaction kinetics experimentally,an activity determination system was established on the basis of ion selective electrodes(ISEs),and a thermodynamic model was used to calculate the activity coefficients of liquid components in data processing to obtain the accurate concentration of ions.The determination in the proposed system is very rapid,and the minimum time interval is only one second.Meanwhile,the determination results are precise and reliable,with maximum deviation less than 2%.The established system was used to study the dissolution process of potassium sulphate and ion exchange reaction of potassium titanate.The effects of solvent and pH were studied.A process may be completed within several minutes.For this rapid process the existing analysis method is unsuitable,while the established system can obtain a large number of data points and the measured results are accurate.The established system and method can also be used in other processes such as dissolution, crystallization,precipitation,ion exchange reaction,adsorption and diffusion for other systems.