1. A control method for an engine, which is executed by a control unit in the engine, comprising the following steps: determining current working status according to basic operation conditions and feature signal values of a plural of sensors, generating expected target values for different targets of the engine under the current working status according to basic parameter maps, correcting the basic parameter maps, and controlling the different targets of the engine; which is characterized in that, during performing the control method for the engine, the control unit also executes the following steps: step S 1 : adaptively learning actual target values fed back by the different targets of the engine and performing comparison and judgment for optimization between the adaptively learned actual target values and the basic parameter maps under the same working status and the same basic operation conditions; wherein, if a condition is not satisfied, the basic parameter maps are kept; and if the condition is satisfied, dynamic parameter maps are generated, and step S 2 : forming combined parameter maps from the basic parameter maps and the dynamic parameter maps, and replacing the basic parameter maps with the combined parameter maps.