There is an increasing demand for more practical while being easy to perform methods to study cell behavior. Here a developed Electric Cell-substrate Impedance Sensor (ECIS) biosensor has been utilized to study different grade of cancerous cells. ECIS biosensor consists of a number pair of gold electrodes in micrometer scale on glass substrate. The impedance is measured by NI DAQ. An equivalent electrical circuit has been developed to model the ECIS behavior in the cell culture. The size of the circuit elements has been calculated by curve fitting method in MATLAB. The impedance of two grades of human colon cancerous cell, HT29 and SW48 has been studied. Previous studies have shown that the expression of adhering molecule has been affected in the cancerous cell. Regarding this studies, cancer can change the cell properties. This changes can occurred in the membrane properties as well as expression of a series of molecule. Impedance spectrometry can detect the changes in cell size as well as adhering properties of cell caused by cancer. Developing this method, it can be used to detect the grade of cancer.