In this study, the antioxidant potential of salicylic acid and its derivatives was determined. O–H bond dissociation enthalpy ionization potential and spin densities were computed, which are important characteristics of antioxidants. We have designed new antioxidants on the basis of information obtained from the results of this study and a literature review. O–H bond dissociation enthalpy, ionization potential, and spin densities of designed compounds were also calculated to analyze the effect of the size of the heterocyclic ring, the electronegativity of the heteroatom, the number of hydroxyl groups, and intramolecular hydrogen bonding. The results reveal that compounds with a larger heterocyclic ring, fewer electronegative atoms, and greater number of hydroxyl groups have enhanced antioxidant activity. A comparison of bond dissociation enthalpy of designed compounds IIIA and IV with that of phenolic acid antioxidants shows that these designed compounds are potent antioxidants. From statistical analysis, it is found that for designed compounds, good correlation was found between spin density and bond dissociation enthalpy. The present theoretical investigation will provide help to understand the biological activity of salicylic acid and its derivatives for better utilization in the fields of pharmacy and the food industry. New antioxidants with better antioxidant activity can be synthesized on the basis of the results of this study.