Abstract: In order to understand the ecological environment and biodiversity maintenance status in the ecological protection red line area of Qionglai Mountain, with satellite remote sensing and topography data, using principal component analysis, the remote sensing ecological index (RSEI) and the biodiversity maintenance function index (BMI) are established. The model is used to monitor and evaluate the ecological environment and biodiversity of the Qionglai Mountain Ecological Protection Redline Area from 2000 to 2019. The results show that the regional average of RSEI from 2000 to 2019 is between 0.642 and 0.680. The southern part of the red line area is mostly high-value area, and the northern part is mostly low-value area. The area with excellent RSEI evaluation level shows a clear upward trend, and the low-value area in the northeast and southwest expand slightly, showing a weak deterioation trend. In terms of biodiverisy maintenance function index, the regional average value is from 0.482 to 0.522 in recent 20 years. The southern part of the red line area is mostly high-value area, and the northern part is mostly low-value area. The overall diversity function showed a slow enhancement. The area with storong functional evaluation grade showed a significant growth trend. In general, the ecological environment and biodiversity of the Qionglai Mountain Ecological Protection Redline Area have improved in most areas, and declined in a small part.