Abstract: Grassland resources are the firm foundation for development of the country's animal husbandry.However, unreasonable development and utilization over the years has caused nearly 90% of the available grassland to experience varying degrees of degradation. Therefore, accurate and timely monitoring of grassland growth and mastering the quality parameters that reflect the growth of grassland are important for grassland management. In recent years, with the continuous development of remote sensing technology, many high-resolution satellites have added red-edge spectrum bands. Because it reflects more clearly on vegetation affected by plant diseases and insect pests, and is less affected by background, it is widely used in vegetation quality

research. Based on the B4 red edge band in Jilin No. 1 remote sensing image, the significant expression characteristics of vegetation are analyzed and studied, and the GQI (Grassland Quality Index) is constructed.Compared with the single vegetation index, this index can more comprehensively measure the advantages and disadvantages of different indicators of grassland quality. The vegetation index with high correlation with grassland quality is calculated. The principal component analysis is carried out to obtain the scoring formula of GQI, and the grassland quality index results are calculated. The results show that the 80% of grassland in Xianghai Nature Reserve is of medium quality and the range of grassland with good growth status accounts for

about 15% , which is more consistent with the actual situation.

Key words: grassland quality index (GQI), vegetation index, red-edge band, principal component analysis