The ionic current rectification, which is a characteristic behavior of asymmetric nanopores, is an important phenomenon, especially in biomolecule analysis. Rectification in nanopores resembles the diode element in electrical circuits, where the ion current is allowed in only one direction. This behavior depends on certain parameters such as pore geometry, the surface charge density of the pore, ionic concentration of electrolyte, applied potential and pressure. In this study, we investigated the rectification behavior of ionic currents in conical pore experimentally and verified the results theoretically. By altering the pH value of the electrolyte solution, we have obtained a variety of current-potential (I-V) curves which have different ion current rectification values. We have compared these values with simulation results and figured out an estimate for the surface charge density of the nanopore walls.