In view of the uncertainty and complexity of decision making problems, as well as the unknown weights of the attributes and the experts, a decision making method based on new preference model and improved cumulative prospect theory is proposed. Firstly, the basic framework of the group decisionmaking problem is defined, and the attribute values and the psychological reference points are improved to the interval values. Secondly, the new preference model is defined according to the twodimensional geometric representation of the interval psychological reference points to determine the attribute weights and the expert weights. Thirdly, the experts’ opinion and psychological behavior are taken into account. Based on the positional relationship between the attribute values and the interval psychological reference points, the formulas of gains and losses are obtained, and then the overall prospect values and ranking relationship of each alternative are determined. Finally, the case analysis and comparison illustrate the validity, feasibility and practicability of the proposed method.