Abstract: The aim of this research is to design a new flow injection analysis unit for the determination of lisinopril through its reaction with NQS at λmax 550 nm. The method involves manufacturing of new valve from a cheap material which can be used in the chemical reactions. The optimum conditions such as sample volume, reagent volume, reagent concentration, flow rate and reaction coil length were studied. Beer’s law is obeyed over the concentration range (5-60 ppm) with linearity coefficient (R2) of 0.9968. The relative standard deviation was 1.094% for 20 ppm lisinopril solution (n = 3). The method was successfully applied for the determination of lisinopril in pharmaceutical formulations and aqueous solution.