The rapid development of urbanization has significantly improved the material standards of living and quality of life for human. However, high-intensity and uncontrolled land development, have led to the degradation of natural ecosystems and a decline in ecosystem services, directly impacting regional ecological security. Constructing an ecological security pattern is an important pathway to control urban sprawl, achieve regional ecological security, and promote social sustainable development. Maintaining a balance between supply and demand of ecosystem services is crucial for ensuring the healthy development and security of ecosystems. Currently, the research on the construction of regional ecological security patterns has gradually formed a basic paradigm of "extraction of ecological source areas-establishment of resistance-surfaces-identification of ecological corridors". Among them, the identification of ecological source areas served as the foundation. However, existing studies lack consideration of the balance between the supply and demand of ecosystem services and the impact of human activities on ecosystem services in the process of identifying ecological source areas. Therefore, it is an important issue to address how to consider the balance between the supply and demand of ecosystem services and incorporate human activities in the identification of ecological source areas when constructing a regional ecological security pattern. As the most populous bay area in the world, the Guangdong-Hong Kong-Macao Greater Bay Area faces a tremendous demand for ecosystem services and encounters significantly ecological security threats brought about by intensive urbanization. This study focuses on the Guangdong-Hong Kong-Macao Greater Bay Area. It initially identifies the ecological source areas based on the balance between the supply and demand of ecosystem services, and determines the final ecological source areas based on the gradient effects of land development on ecosystem services. Subsequently, an ecological resistance surface is constructed based on habitat quality. Using circuit theory, the ecological corridors and key nodes are extracted, ultimately establishing the ecological security pattern of the Greater Bay Area. The findings of our study are as follows: (1) the spatial matching degree of ecosystem service supply and demand exhibits a weak correlation. Specifically, this manifests as high supply and low demand in the surrounding regions, while the central area experiences high demand and low supply. The regions with the highest comprehensive supply and supply-demand ratio of ecosystem services are primarily located in the peripheral areas with high vegetation coverage. (2) The comprehensive supply of ecosystem services within the research area demonstrates a significant decline corresponding to the degree of land development. Moreover, a notable threshold point (28.27% of land development) is observed, beyond which the comprehensive supply of ecosystem services experiences a rapid decrease. (3) In total, the research area encompasses 100 ecological source sites, spanning a total area of 7344.24 km². The distribution pattern of these sites exhibits a peripheral surrounding structure characterized by a higher concentration in the eastern and western regions and a sparser distribution in the central region. (4) A network of 175 ecological corridors, measuring a total length of 1568.48 km, is identified within the research area. These corridors primarily adopt a circular distribution pattern. (5) The research area presents 40 ecological pinch points and 19 barrier points, primarily influenced by the length of corridors and the distribution of cultivated and construction land. Collectively, these key ecological elements compose a circular ecological barrier encircling the Guangdong-Hong Kong-Macao Greater Bay Area.