The invention discloses an SCR system urea injection control method based on an H infinite feedback gain pulse spectrum table, which belongs to the technical field of diesel engine urea SCR discharge post-processing system control. According to the invention, linear system H infinite state feedback and the multi-operating point gain pulse spectrum table are combined; the control demand of a nonlinear system in real industry is met; and the design advantages of an H infinite state feedback control theory is used. The existing LMI toolbox is reasonably used to solve an optimization problem offline. The calculation amount of an online control system can be reduced. The method has the advantages of simple derivation process and high practicality, and can provide a way for the design of a vehicle-mounted control system.