Taking Beijing as an example, the granularity back-calculation method and the landscape connectivity index were combined to identify important ecological land. The neighborhood analysis was adopted to construct the ecological resistance surface, whereas the minimum cumulative resistance model was used to construct the ecological security pattern. The probability of land expansion calculated through an artificial neural network was used to classify the ecological security pattern of construction. The results show that the important ecological land area of Beijing is 6488.53 km², mainly distributed in the mountainous areas of western and northeastern Beijing, and a small part is located in the southeast plain area. The primary protection ecological land area is 4482.48 km², mainly distributed in the northwest and southwest. The secondary protection ecological land area is 1338.27 km², which is mainly distributed in the western suburbs, the suburban plains in the southwest and the plains in the southeast. The third-level protection ecological land area is 669.77 km², mainly distributed in the north-central and southeast plains. The important ecological corridor is 2410.47 km long and is distributed in the outer suburbs and urban-rural junction. Among them, the length of the first-class ecological corridor is 1477.63 km, mainly distributed in the mountainous areas of the northwest and southwestern suburbs; the secondary ecological corridor is 390.91 km, which is mainly distributed near the ecological land of the outer suburb plain; the third-level ecological corridor is 541.93 km, mainly distributed in the surrounding area of the city center, surrounded by the central city.