According to the emotion of episodic prospection hypothesis, the present study attempted to use a 3 (prospective emotional valence: positive, negative, neutral) × 2 (group: training, control) × 2 (test time: pre, post) mixed design to investigate the effect of episodic prospective ability on delay discounting. The results showed that: 1) The stronger the episodic prospective ability, the greater the degree of change in delay discounting rate. 2) This process was also moderated by prospective emotional valence, that is, positive prospective emotion decreased delay discounting rate, and negative prospective emotion increased delay discounting rate. These results illustrate that episodic prospective ability influences the extent of delay discounting rate, whereas prospective emotional valence moderates the direction of delay discounting.