Models of decision making usually focus on cognitive, situational, and socio-cultural variables in accounting for human performance. However, emotion especially immediate emotion is rarely addressed within these models. This paper proposes an emotion-based cognitive model about how decisions are made which unifies emotion and cognition as two symbiotically integrated aspects of intelligent behavior. Within the general computational framework the influence of both immediate emotion and expected emotion are included. And to deal with the Zajone-Lazarus controversy concerns whether emotion depends upon appraisal of a situation or is triggered directly by stimulus features, the present study fits the compromise interpretation that there are parallel processes involved in the triggering of emotion. We also give a formalized description of the model to make it computable and illustrate it by an example of taxpayer's reporting decision.