In order to develop a sensing platform, it is very important to understand the sensing mechanism of the modified electrode by locating the redox reactive sites of the modifier, for this better understanding we used the density functional theory (DFT)-based quantum chemical modelling to explain the redox reactive sites of the pyrogallol red molecule. The pyrogallol red was later used to modify the carbon paste electrode by electropolymerisation technique for sensing applications. The real analytical applicability of the proposed sensor was evaluated by employing it to the analysis of pharmaceutical sample and a good recovery results were obtained. According to the experimental results, a high reactivity performance is observed at the fabricated electrode for the paracetamol (PRM) electro-oxidation involving the transfer of identical number of electrons and protons. The lower limit of detection (LOD) was 0.11 mu M by differential pulse voltammetric (DPV) method in the linear range of 5.0 mu M 45.0 mu M was obtained. The real analytical applicability of the proposed method is valid for the pharmaceutical analysis in presence of possible excipients suggested that the fabricated electrode is a promising sensing platform. The methodology adopted in the present work can be extended to construct the electrochemical sensor for other electroactive molecules also.