Considering recent widespread applications in nanofluidics, we analyze the ionic current in a pH-regulated nanochannel, using an aqueous NaCl solution in an SiO2 nanochannel with pH adjusted by HCl and NaOH as an example. The model assumed is closer to reality than that in previous analyses, where the channel surface is maintained either at constant potential or constant charge, and only ionic species coming from background salt are considered. The electrical potential, velocity distribution, and ionic current under various conditions are examined by varying the pH, the density of surface functional groups, and the background salt concentration. We show that neglecting ionic species other than those from back ground salt might yield appreciable deviation in ionic current. The mechanisms involved in ionic transport are discussed, and we show that the effects of double-layer thickness and surface potential yield complicated and interesting behaviors in ionic current.