Previous studies investigating the relationships between emotional state and creativity reveal inconsistent and inconclusive results. Some found that positive emotional state enhanced creativity performance; some supported the facilitative effect of negative emotions; while others showed that positive and negative emotional states can both improve creativity. These inconsistencies might be attributed to the problems that the lack of differentiation between levels of emotional states and no distinction is made between different types of creativity tasks in the previous studies. According to achievement motivation theory, optimal arousal level is a U-shaped function of the nature of performance task, and different tasks require different levels of arousal for optimal performance. Past research also indicated that different creativity tasks, says, open-ended divergent thinking and closed-ended insight problem solving, involved distinct processes. In the present study, 200 participants were randomly assigned to five emotional manipulation conditions – high degree of positive emotion, medium degree of positive emotion, neutral, medium degree of negative emotion, and high degree of negative emotion. Half of the participants in each condition performed divergent thinking test, while the other half performed insight problem-solving task. The Results showed that different emotional states have different effects on the two creativity measures. While medium positive emotional state can mostly improve insight problem solving, divergent thinking performance is positively related to the degree of arousal-regardless of positive or negative valence, – the higher the emotional arousal, the more enhanced the performance. These Results help to clarify the relationships between emotion and creativity. Results also establish the basis to explore the mechanism by which emotions influence creativity and the means by which creativity can be enhanced.