Abstract: The poignant conflict between the rapid-growing population and the keeping-decreasing cultivated land has made the research on the dynamic monitoring system of cultivated land receive more and more attention. The early-warning system of cultivated land is the important portion of the dynamic monitoring system of cultivated land. Its purpose is to forecast the cultivated land system quantity and quality changes which exceed the critical value of space-time scope and dangerous degree, through analyzing the relevant factors of nature, society, economy and policy, which affect the farmland-developing situation. On the basis of ensuring the safety of food supplies, the early-warning system of cultivated land can alert the cultivated land situation to meet the need of society and economy development in the area during the period. At the same time it discusses the evolvement mechanism of cultivated land system, puts forward the amending scheme, monitors the system to avoid the grave depravation of the resource of cultivated land, supplies the service of the real-time data and model for the sustainable use manage of land and the actualization of the dynamic balance maintenance of total cultivated land. The strategic ultimate aim of the dynamic balance maintenance of total cultivated land is to ensure the safety of food supplies and to make the output capacity of deposit cultivated land and the output level per person increase. In fact, the urban expansion is the process during which the urban land system captures the cultivated land of the combination zone between urban and rural area. As the perceptive sensitivity of urban land system and the cultivated land system, the cultivated land price affects the captive force. The occupation cost of cultivated land is low; the social influence of cultivated land loss is not brought into the market cost. Both of these lead to low comparative benefit of cultivated land, which are the deep reasons of cultivated land loss. The social influence of cultivated land reflects the safeguard ability of corn security. From the dynamic balance of the total quantity of the cultivated land, the cultivated land alarming degree, which is judged by the cultivated land early-warning system, reflects the safeguard ability. During the cultivated land non-agricultural process, the critical alertness is taken for the cultivated land loss; the correct coefficient of the alarming degree is set up to modify the cultivated land price at the same time. The critical alertness of cultivated land and alarming modification of cultivated land non-agriculture cost should be founded on the classifying work of cultivated land. Based on the second general soil survey data, long-period soil monitoring data and relevant statistical data of cultivated land condition, integrated with the analysis of cultivated land investigation in typical area, an indicator system and warning model of cultivated land early-warning system of Xishan City are set up. According to this model, the analysis of the early-warning for the cultivated land of Xishan City is performed. The computation methods of the determinative coefficient of the cultivated land alarming degree and the correct coefficient of the cultivated land non-agricultural price are given in this paper.