The purpose of this study is to review about the Series Elastic Actuator (SEA), which analyses the theoretical and experimental results of impedance control, stiffness, torque control, energy consumes to generate the actuator.Normally the torque control of SEA depends on the spring and the amount of current giving in from the motor to generate the actuator.The stiffness in SEA also depends on the spring where many customize the spring according to the experimental needs.Impedance control is important because of the importance of interactions with the human body.This SEA largely used in robotic rehabilitation field since it has one of the best actuation techniques where the manufacturer can customize them according to their needs.SEAs are easy to manufacture, light, low cost and can be safely used in human operations without any major safety requirements.A new design was introduced to improve the range of motion and to have better torque control. © 2023, Institute of Technology PETRONAS Sdn Bhd.