Demarcation of ecological protection red line is an important measure to ensure the ecological security. It is conducive to maintain the integrity of the ecosystem and achieving the sustainable development. Based on the ecosystem function and ecological sensitivity, an ecological security pattern was constructed for Qilu Lake watershed. This paper demarcates and administers the ecological protection red line. We revealed that:(1) The extremely important regions of sub-elements are superimposed to obtain the extremely important regions of ecosystem function. Zhewan River, Changsha River, Dasha River and mountainous areas have the highest ecological sensitivity, the dam area has higher ecological sensitivity. (2) The red line of first-level ecological protection covers areas of extremely important and sensitive ecology, lake shorelines and reservoirs. The red line of secondary ecological protection covers the ecological buffer zone around the lake, the ecological buffer zone in mountainous areas and the ecological corridor dominated by rivers. The three-level ecological protection red line covers the ecological coordination area, mainly farmland. (3) Ecological restoration should be adopted to protect the ecological functions of the extremely sensitive areas within the red line of first-level ecological protection. The red line for secondary ecological protection focuses on ecological protection to maintain the ecological quality of the region. Overall optimization of the three-level ecological protection red line should be carried out to improve the carrying capacity of the ecological environment.