Although previous studies showed that episodic prospection affected delay discounting,the cognitive mechanism of episodic prospection affecting delay discounting is still unclear.The present research explored how episodic prospection modulated delay discounting.Study 1 showed that participants were more inclined to choose the delayedbut larger rewards when they imaged positive future events than when they did not image events; Study 2 showed that participants were more inclined to choose the immediate but smaller rewards when they imaged negative future events than when they did not image events; In contrast,study 3 showed that choice preferences of participants when they imaged routine future events were the same as when they did not image events.Our findings suggested that episodic prospection might modulate delay discounting by emotion.Furthermore,the valence of imaged future events’ emotion might play an important role in individuals’ intertemporal choice.