Carbon nanotube (CNT) integrated with biological functionalities is expected to be one of the most promising field in future biomedical applications. CNT material with prominent properties along with application of micro fabrication technology make possible enormous application potential sensors with high resolution, more accurate, higher sensitivity and micrometer size. One of these applications, introduced in this paper, is pH sensors using CNT as sensing material. Monitoring and evaluating the pH of the solution in a bioprocess is one of the key steps in the success of bioreactor operation. Our proposal based on the changes significantly in electrical property of CNT under different pH environment. This paper describes a method for designing a simple and fast response pH sensor employing single wall carbon nanotube (SWCNT) using a spray. The conductance and the typical amperometric respond of SWCNT at room temperature at different hydroxyl ion concentrations were successfully demonstrated.