In the analysis of travelers¡¦ decision-making behavior, Discrete Choice model in Revealed Preference data or Stated Preference data, such as logit model and probit model, is generally used in the exploration of travelers¡¦ mode choice behavior. Some former research adapted Structural Equation Model (SEM) or Fuzzy Theory in exploring the variables of travelers¡¦ psychological decision process, because the variables which were not easily measured directly and tend to be latent variables.This study combines Theory of Planned Behavior (TPB) and EMB Model in consumer behavior science, to investigate the relationship and degree of interaction between psychological variables and actual mode choice behavior. The comuter represent high percentage of inter-city transportation, therefore, this empirical study has focused on the commuters in Taipei metropolitan area. Commuter¡¦s feedback on MRT preference was collected through the face-to-face interview. The collected data was analyzed by using SPSS10.0 for chi-square test, the regression analysis and multi-variables analysis. Through the study of their attitude, the degree of involvement, group affection and intention towards various modes, the psychological decision process for commuter was analyzed and concluded. The results of the research concluded that: private transportation users have higher degree of involvement to MRT than the public ones. It is observed that the variables of age, occupation, possession of veheche, the distance from commutes' place to MRT station, among all variables, have significant reciprocity with the degree of involvement for MRT.In the aspects the commuters' attitude of using the MRT¡¦s, both private and public transportation users showed positive opinions. Among all variables, the group influence had the least significance to the action intention, while the involvement and attitude showed high significance to the MRT¡¦s action intention.The public transportation users show higher difference between actual mode use behavior and intention, as compared to the private one. Therefore, the traffic authorities and businessman need to increase the quality of the service of MRT and convience of transfer between transportation modes, if they want to raise the percentage of commuters to using MRT.