This paper describes the use of nanosensor and pH-dependent fluorescent dye to monitor intracellular pH in single CA46 cell. The pH-dependent fluorescent dye 5 (6)-Carboxyeosin diacetate (CFDA) was used to measure intracellular pH from the surface fluorescence of the single CA46 Cell. Argon ion laser was focused on single cell with a fiber optic nanoprobe which is parked outside on the single cell, also the emitted light was collected with this fiber optic nanoprobe. To account for system instabilities, we have explored a ratiometric approach to determine the intracellular pH on the single-cell level after staining with CFDA. Calibration of the intracellular fluorescence spectra is obtained by equilibration of internal and external pH with Nigericin in k+ buffers at different external pH. Besides accurate estimated of intracellular pH (7.21?0.05). This technique permitted monitor transient changes in intracellular pH caused by addition and removal of NH4+ and allow to study pH-regulatory in Single CA46 cell.