Abstract: A novel flat-headed pH electrode with flow injection technique was applied to the potentio-titrimetric determination of concentration of solutions of strong bases (e.g. NaOH solution) and weak bases (e.g., aqueous ammonia), with HCl solution used as titrant. Working parameters for the FIA system selected were: ① length of mixing coil: 40 cm; ② concn. of HCl solution (as carrier): 1.027×10-3mol·L-1; ③ sampling volume: 310 μL and ④ flow-rate: 0.82 mL·min-1. Linear relationships of values of peak area, peak height and half peak width with logarithm of concentration of NaOH or aqua ammonia solutions were obtained in definite ranges. The proposed method was used in the analysis of samples of basic solutions, the sensitivity of this method was ten times higher than that of the manual titration method, and values of RSD′s (n=5) found were in the range of 1.1%-1.8%.