In view of the redundancy of trust sources and the fact that the interference between them is not considered in the existing trust measure models, a decision model based on trust measure considering interference effect in a social network is proposed. When calculating the trust value between decision-makers, this model simplifies the types of trust sources, avoids the overlapping of some trust sources, and increases the interference item between trust sources. Firstly, the sources of trust between decision-makers are divided into ``close relationships between decision-makers'' and ``objective backgrounds of decision-makers'' according to the determination of social relationship and background on trust. Secondly, the concepts of ``closeness degree'' and ``professionalism'' are proposed as the measures of these two trust sources to ensure that the defect of redundancy can be overcome on the premise of integrity of trust sources. Then, a trust value quantification method considering the interference effect is further designed. The trust value can comprehensively reflect the individual decision degree and the overall influence degree of trust sources. Finally, the trust values of decision-makers are transformed into weights to aggregate the preferences of decision-makers to solve the actual group decision-making problem. Numerical and theoretical results show that the proposed trust measure method considering the interference effect can be used as a tool to improve the accuracy of trust relations and solve the group decision-making problems in social networks, which has a broad application prospect.