1. In the northwest semi-arid area, with the population growth, natural landscape is replaced by artificial landscape, habitat is broken, landscape connectivity is worse, biodiversity is reduced, land desertification is serious, soil is eroded, and the frequency of sandstorm weather is increased.

2. Whether the planning objectives and construction tasks of key forestry ecological projects can be completed with high efficiency, high quality and high benefit, and the contribution of forestry projects to improving the spatial ecological network and landscape pattern are related to whether a well-off society marked by good ecology and harmonious development between man and nature can be realized. Constructing multi-level spatial ecological network is an important guarantee for maintaining ecological security in semi-arid areas of western China. The stability of low-level ecological sources depends on high-level ecological sources, which is of great significance to maintain the stability of hierarchical ecological networks.

3. The destruction of high-level ecological sources can easily affect the surrounding low-level ecological sources, thus affecting the stability of low-level ecological networks, causing cascading failure of hierarchical networks and leading to the collapse of the whole network. Taking a city in northwest China as the research area, with the support of GIS spatial technology, the hierarchical ecological network of a certain place is extracted by using the analysis method of landscape ecology principle and complex network theory, and the spatial structure and topological structure of the network are studied.