Aiming at the problem of large-scale multi-attribute group decision making, it is difficult to determine the preference weights of decision makers under the unbalanced hesitant fuzzy language environment. A method for calculating the preference weights of individual decision makers in the same fuzzy cluster is proposed. First, under the unbalanced hesitant fuzzy language environment, the concept of the preference weight of a single decision maker in the same cluster is introduced. Then, on the basis of the FCM algorithm, the cluster center generated by the algorithm and the membership of the decision maker and the cluster are used. It defines a new preference weight calculation formula and a cluster’s decision matrix calculation formula, thereby obtaining a new large-scale group decision-making method. Finally, an example is used to verify the feasibility and effectiveness of this method.