The invention discloses a decomposing furnace outlet temperature modeling method, and belongs to the field of industrial automation. The method comprises the following steps: firstly according to the cement pre-decomposition technological process and experiences of field operation personnel, selecting a coal feeding amount and a raw material feeding amount as input variables of a model; according to historical data, establishing mathematic models of various working points; when the decomposing furnace outlet temperature is 830 DEG C and 840 DEG C, using a least square learning algorithm to model, and when the temperature is 850 DEG C and 860 DEG C, adopting a learning algorithm of an extreme learning machine to model; at last, according to the experiences, dividing membership function curves, and establishing the decomposing furnace outlet temperature mathematic model based on T-S fuzzy control. The decomposing furnace outlet temperature modeling method disclosed by the invention can accurately reflect the decomposing furnace outlet temperature variation trend, and lays a foundation for realizing optimized control of the decomposing furnace.