Revealing the dynamic biological flow between eastern and western China from the perspective of ecological network

China is one of the most biodiversity-rich countries, yet the ecological gap between its eastern and western regions, driven by geographical barriers, restricts species migration and disrupts ecosystem connectivity. However, the potential of biological flow to bridge this divide remains poorly understood. To address this, we developed a dynamic biological flow framework, combining ecological networks with two new tools, Ecological Linkage Tool Direction and Biological Flow, to quantify species migration directions and intensities across the Middle Spine of Beautiful China. Within and beyond ecological sources, we analyze dynamic biological flow and network structure at node, link, and graph levels. We also simulate changes in network efficiency under various corridor and habitat degradation scenarios. Among the 13,800 ecological corridors, 27 % are oriented east-west (EW), yet the region exhibits a net negative habitat inflow, with 48 % of migrating species potentially failing to reach target habitats. Biological flows outside habitats follow west-to-east (21 %) and north-to-south (18 %) patterns, with the highest migration losses occurring in the north-to-south direction. The regional network efficiency is 0.053. The failure of ecological network in the Inner Mongolia Pastoral Area reduces efficiency by 24 %, intra-patch EW corridors by 57 %, and inter-patch west-to-east corridors by 13 %. Species-specific analyses of the red panda (Ailurus fulgens) and Chinese horseshoe bat (Rhinolophus sinicus) reveals that habitat distribution determines dynamic flow direction, while species-specific adaptability influences flow intensity. This study quantifies dynamic biological flow patterns, overcoming the limitations of widely used static distribution-based conservation planning, more accurately reflecting species migration traits.