Abstract: The proposition of the compartment model method brings us bopes that with this method We can solve she problem of matter cycling in agroecosystem quantitatively. In this paper based on data collected in our experiments and surveys a compartment model Was built, and the behavior of agroarosystem in nutrient cycling was simulated and predicted using computer for Doudian village in Beijing suburb, With the model tested in different decisions. It Was proved mathematically that the system Was tending lottfards a steady state and was observable as Well as coutrolable. Sensitivity of the system to perturbation Was highest with N and decreasing with P and K respectively. Recycling indicis of NPK in the system Were computed as a scientific basis provided for Ihe system management. The method of building a compartment model Was discussed in the paper, which suggests an improved modification of syslem analysis, with its shortcomings and limitations indicated.