A sequential injection analysis (SIA) system for the determination of SCN -ion using a microfluidic polymer chip with an embedded SCN -ion-selective electrode (SCN --ISE) as a detector was developed. Under the optimal flow conditions of the SIA system, the SCN --ISE showed a good linear relationship between peak heights and logarithmic concentrations of SCN -ion with a Nernstian slope of 59.4 ± 3.8 mV decade -1 in a concentration range from 1.0 × 10 -5 to 1.0 × 10 -1 mol dm -3 . Sample throughput of the present system for the determination of SCN -ion was approximately 12 samples h -1. The proposed SIA system was applied to the determination of the level of SCN -ion in human saliva samples.