A determination method of cyanide ion (CN-) using nickel complexation reaction by continuous monitoring system. The mechanical parameters and chemical conditions of the complexation reaction were investigated prior to application of continuous monitoring system for determination of cyanide. On the optimized conditions, the calibration curve was linear over the range from 5.0×10^(-6) to 1.0×10^(-4) M. In this range, 2.40% of the reproducibility (RSD, n=3) was obtained. The limit of detection (3σ/s) was calculated to be 1.8×10^(-6) M.