The oxidative polycondensation reaction conditions of 4-[(2-hydroxyl-1-naphthyl)methylene]aminobenzoic acid (4-HNMABA) with H2O2, air O2 and NaOCl were studied in an aqueous alkaline medium between 40°C and 90°C. The structure of oligo {4-[(2-hydroxyl-1-naphthyl)methylene]aminobenzoic acid} (O-4-HNMABA) was characterized by using 1H-NMR, 13C-NMR, FT-IR, UV-Vis, size exclusion chromatography (SEC) and elemental analysis techniques. At the optimum reaction conditions, the yield of O-4-HNMABA was found to be 70% for H2O2 oxidant, 94% for air O2 oxidant and 87% for NaOCl oxidant. According to the SEC analysis, the number-average molecular weight (Mn), weight-average molecular weight (Mw) and polydispersity index (PDI) values of O-4-HNMABA were found to be 850, 1350 and 1.59, using H2O2, 1800, 2200 and 1.22, using air O2 and 2200, 3000 and 1.36, using NaOCl, respectively. TGA-DTA analyses showed that O-4-HNMABA was more stable than 4-HNMABA. The highest occupied molecular orbital, the lowest unoccupied molecular orbital and electrochemical energy gaps ( ) of 4-HNMABA and O-4-HNMABA were found to be -6.34, -6.56; -2.67, -3.04; 3.67 and 3.52 eV, respectively, by cyclic voltammetry (CV). According to UV-Vis measurements, optical band gaps (Eg) of 4-HNMABA and O-4-HNMABA were found to be 3.12 and 3.03 eV, respectively.