The purpose of this research was to develop a test kit for determination of chloride in water on the reaction between mercurythiocyanate and chloride with iron (III) nitrate which provided an orange complex compound. The color of the orange complex compound was then comparied to the color scale. This test kit could examine chloride concentration in a range of 10 – 300 ppm. Moreover, the effect of various interference which were pH Mg2+,K+,SO4 2-,NO3 , NH4,PO4 3-Ni2+, Cd, Hg, Cu2+,Na2+, Fe2+ shelf life and temperature also studied. The result showed that pH had no effect on the reaction except morethan pH 13. The interference of Mg2+,K+,SO4 2-,NO3 , NH4,PO43-Ni2+, Cd, Hg, Cu2+,Na2+, Fe2+at the concentration in a range of 0.04 ppm - 4 ppm had little impact on the reaction but at the concentration morethan 50 ppm all interferences impacted on the reaction. The developed test kit could be stored at 4 °C room temperature 50°C for morethan 90 days. The accuracy the test kit tested with uv-visible spectrophometry revealed that the results of the two methods were nearly the same.