The invention belongs to the SCR system ammonia spraying amount regulation and control field and discloses a method for regulating and controlling an ammonia spraying amount based on inlet NOx concentration prediction. The method comprises the following steps of (a) measuring and acquiring a measured value of each correlation parameter at a current moment and an inlet NOx concentration respectively; (b) according to a relation between the correlation parameter and the inlet NOx concentration, constructing a prediction model and predicting the inlet NOx concentration of a next moment; (c) carrying out filtering processing on the inlet NOx concentration of the current moment, and taking a difference value of the filtered inlet NOx concentration and the inlet NOx concentration of the next moment as a predicted variation value; and (d) taking the predicted variation value and the like as input of a denitration system PID controller, and outputting an ammonia spraying valve opening degree so as to complete regulation and control of the ammonia spraying amount. In the invention, the prediction model is used to predict the inlet NOx concentration of the next moment, the ammonia spraying amount is optimized, a frequent fluctuation of an outlet NOx concentration is restrained and adjusting quality of the outlet NOx concentration is increased.