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 plurality 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; wherein the basic parameter maps are corrected according to a correction strategy, comprising the following steps: correcting the basic parameter maps using the feature signal values of a plurality of associated sensors which reflect the current working status of the engine; correcting the basic parameter maps using soft measuring feature signal values which are obtained by performing a soft measuring method with a new feature signal processing way of the associated sensors on the variables that can't be directly measured; and correcting the basic parameter maps using the feature signal values of the associated sensors which are adaptively learned by performing weighted value matching during the correction step between the expected target values and the actual target values; wherein, the feature signals of the associated sensors comprise the signals of the associated sensors of the engine and the feature signals deduced using soft measuring way, including a crankshaft position and rotational speed signal of the engine, a top dead center signal, a torque signal, an injection pulse width signal, a throttle valve position signal, an oxygen sensor signal, a fuel temperature signal, a machine oil temperature signal, an environment pressure signal, a power supply loop voltage signal, a water temperature sensor signal, an exhaust temperature signal, an intake pressure signal, an air-fuel ratio signal, a knock signal, a flame conduction angle signal, frequency selection probability distribution of knock signals in several cycles, and probability of a flame transmitting angle signal exceeding time threshold.