Forecast of agricultural machinery equipment level is a complicated non-linear system, whose developmental changes have dual treads of continuity and fluctuation. SW—GP (sliding window—genetic programming) algorithm was provided to implement automatic modeling of dynamic forecast function of agricultural machinery equipment level. In the program, sampling data is obtained by sliding window technology and model is founded automatically by GP-improved algorithm, which can overcome the difficulties of model selection in traditional prediction modeling methods. The results of a computation case show that forecasting values from the model agree well with the real values, which explains that employing SW-GP modeling can settle problem for the modeling of complex agricultural machinery equipment level forecast system satisfactorily.  