The purpose of this study was to develop and verify the smart insole based FSR sensor for measurement and improvement of the muscle strength imbalance. We recruited 15 subjects with muscle strength difference over 20% and 15 subjects with muscle strength balance below 10%. We developed the human body load insole and integrated modules using FSR sensor. Subjects walked for 5 minutes at a slope of 0% and a speed of 3 km / h on a treadmill with a smart insole. We measured the real-time muscle activity and foot pressure according to the muscle strength imbalance during gait. FSR data of the developed smart insole showed that the insole had similar accuracy and efficacy as muscle activity and foot pressure. This is the interval in which the muscle imbalance shifts from the stance phase to the load reaction, and the weight support is the largest, and the center of gravity of the human body passes over the whole foot, which is considered to cause the greatest imbalance. This suggests that there is a direct or indirect correlation between muscle strength imbalance of the lower limb and the imbalance of the body weight distribution during gait.