Series　elastic　actuator　is　a　very　effective　actuation　method,　which　is　suitable　for　force　control　applications　inter-acting　with　ambient　intelligence.　The　actuator　is　distinguished　by　an　elastomer　which　placed　in　the　transmission　system.　However,　due　to　spring　fatigue　and　joint　friction,　there　are　clearances　in　the　actuator　transmission,　which　will　greatly　affect　its　output　performance.　Therefore,　we　firstly　developed　an　exoskeleton　crank-slider　series　elastic　actuator,　and　then　established　a　simplified　mathematical　model　of　the　actuator　with　clearance　joints.　Finally,　the　impact　of　clearance　on　the　dynamic　behavior　and　nonlinear　response　of　the　mechanism　is　explored　by　numerical　simulation.　The　results　show　that　the　output　of　the　mechanism　lags　behind　due　to　the　clearance,　and　with　the　increase　of　the　hysteresis　effect,　the　mechanism　will　appear　chaotic　behavior.　©　2022　IEEE.