The invention relates to the technical field of cement firing, and discloses a decomposition furnace coal feeding quantity control system and method based on decomposition furnace outlet temperature prediction, a characteristic point standard set obtained based on a time-delay cross-correlation method is utilized to construct a historical training sample, a model is trained according to the historical training sample, and a decomposition furnace outlet temperature prediction model is obtained; establishing a mapping relation from the coal air combination factor to the outlet temperature of the future decomposition furnace; constructing a tailing coal feeding quantity control model to deduce a tailing coal feeding quantity given value of the decomposing furnace in the next time step on the basis of predicting the outlet temperature of the decomposing furnace; real-time data corresponding to the feature point standard set are obtained, and coal feeding amount adjustment is conducted according to the given value, obtained through the model, of the tailing coal feeding amount of the decomposing furnace in the next time step; and performing decomposition furnace outlet temperature prediction effect monitoring and tailing coal feeding quantity optimization effect monitoring according to the operation condition after the tailing coal feeding quantity is adjusted, and dynamically updating the decomposition furnace outlet temperature prediction model and the tailing coal feeding quantity control model according to the monitoring result.