In order to effectively solve multiple attribute group decision-making problem under the interval type-2 fuzzy environment, the interval type-2 fuzzy language Z - Numbers (IT2FLZNs) has been proposed, which is used to express the objective information of natural language and the trust degree of information. First of all, IT2FLZNs and its operation properties are defined based on the interval type-2 fuzzy set and Z - numbers theory. The similarity and distance between the IT2FLZNs are proposed. Secondly, in the case of unknown experts and attribute weights, according to the principle of the minimum overall uncertainty in decision making, the optimization model is constructed by using similarity to determine the weight of experts and attributes, and the optimal scheme is selected by comparing the group utility value, individual regret value and intimacy of each scheme. Finally, a case of bank liquidity risk is used to verify the effectiveness and feasibility of the proposed method.