According to the undoing effect of positive emotions, positive emotions are hypothesized to undo the cardiovascular response after experiencing negative emotions. However, existing evidences have shown divergent results regarding the undoing hypothesis. The author tends to integrate present research findings into a coherent theory trough exploring the effects of emotional arousal on the undoing process. A laboratory study was designed to investigate the effects of different arousal level of positive emotions on cardiovascular recovery in laboratory. Results showed that high-arousal and low-arousal positive emotions predict differently on cardiovascular recovery.