[Objective] The spatial relationship between cultivated lands and construction project distributions was analyzed, and a method for defining the upper thresholds of cultivated land proportions in construction project areas was determined in order to provide references for formulating measures of protecting cultivated land. [Methods] The study was conducted in Shaanxi Province. An index of cultivated land density was constructed based on land change survey data and construction project samples. With the integration of GIS spatial overlaying, geomorphic zoning, and statistical analysis methods, intensity zoning of cultivated lands in Shaanxi Province was presented and the upper thresholds of cultivated land proportions in construction project areas were determined. [Results] Using a method that combined geomorphic zoning with administrative unit revision, and taking the 80% cumulative frequency value as the thresholds, Shaanxi Province was divided into three zones of cultivated land density, including North Shaanxi Loess Plateau-intensive cultivated land, Guanzhong Plain/Qinba Mountain-intensive cultivated land, and other districts (non-intensive cultivated land). The upper thresholds of cultivated land proportions in linear project areas and in planar project areas in the three zones were determined to be 26%, 42%, 20%, and 45%, 80%, 27%, respectively. The proportion of cultivated land in construction projects in the districts of intensive cultivated land was significantly higher than in the districts of non-intensive cultivated land, showing that greater density of cultivated land led to a higher proportion of cultivated land in construction project areas. [Conclusion] By defining the upper threshold of the proportion of cultivated land occupied by construction projects, the cultivated land saving rate can range from 1.2% to 17.9%, which could control 13.9%—22.5% of construction projects against excessive occupation of cultivated land, thereby effectively protecting cultivated land resources.