An optimization design simulating the electro-mechanical property of the conductive elastic knitted fabric is built based on a loops structure under biaxial extensions. A computer program can give the fabric equivalent resistance, which is obtained by solving the circuit network equations. So, it can simplify the computational process immensely. In order to simplify the calculation of the contacting forces on the overlapped yarns, two hooked yarns are used to represent the loop configurations. From the theoretical analysis and experimental investigations, it is found that the resistance changing due to the yarn segment transfer is the key factor for the sensitivity of elastic fabric sensors. This makes the resistance linear increasing with the strain increasing. Analysis of the experimental results show that change in the resistance of a fabric sensor due to the contact resistance has a minor contribution to the sensitivity of the sensor in the large-strain regime. Also, the fabric structure and the yarn elongating affect the characteristics of the fabric sensor.