a process for fabricating a whole solid - state ph sensing device by using the polypyrrole as the contrast ph detector and a whole solid - state ph sensing device fabricated by the process are disclosed , wherein said device is a differential pair framework potential electrochemical sensing device fabricated by using a non - insulating solid - state inorganic ion - sensing membrane and a polypyrrole sensing membrane . the largest difference between the device of the present invention and the conventional potentiometric type ph sensor is that the sensor of the invention is a solid - state planar sensor . the differential pair framework uses tin dioxide as the ion - sensing membrane and the reference electrode , and uses a polypyrrole sensor as the differential sensor , wherein the sensitivity of tin dioxide is good and has a value up to 57 mv / ph , and the sensitivity of polypyrrole is about 27 mv / ph . these lead the sensitivity of the whole solid - state ph sensing device to a value of 30 mv / ph and exhibits good linearity , so that the sensing device framework has practicability . since the sensitivity of the polypyrrole can be controlled by means of its polymerization , a sensing device with controllable sensitivity can be fabricated for applying to the fabrication of a ph sensor or a biosensor .