This study employs the tin oxide (SnO 2 ) films as the sensing membrane for fabricating array sensors and combines these sensors with a real-time sensing system. Furthermore, the four-point probe, X-ray diffraction (XRD) and scanning probe microscopy (SPM) were applied in identifying the surface characterization of the SnO 2 pH electrode. This study presents an array pH sensing system to obtain the signals from the SnO 2 pH electrode. Additionally, an array sensing system reduces the errors of the single sensor and the real-time sensing system is employed as the testing system to reduce testing time. This paper presents the real-time sensing system that includes eight readout circuits and one data acquisition card using software (Labview) to control. Experimental results proved the surface characterization of the SnO 2 pH electrode and this pH sensing system that monitored signals from each sensor simultaneously. Therefore, this paper presents an efficient real-time pH sensing system for array sensors.