In this study, electrochemical graphene (ECG) was chosen to be attached to a polyester fabric with a knitted structure as a flexible fabric strain sensor through a cloth dyeing method. According to scanning electron microscopy observation and Raman scattering spectroscopy measurements, ECG was successfully attached to the fabric structure. The electromechanical performance and strain sensing properties of the graphene-based flexible strain sensor were evaluated. The resistance change and gauge factor of different ECG attached as a fabric strain sensor were quantified. The gauge factor of the fabric strain sensor with less ECG is greater than that of the fabric strain sensor with more ECG. The high gauge factor of 47 was achieved in a strain range from 0% to 2%. The fabricated strain sensor exhibited high sensitivity, fast response time and good repeatability. The fabricated ECG fabric strain sensor could be used to detect tiny physiological signals and human motion.