Abstract: Taking the ‘Marselan’ grape of Zhangye area in 2021 as the test material, the quality evaluation and classification of ‘Marselan’ grape of different harvesting periods were carried out by principal component analysis and K-means clustering analysis method, and the optimal harvest date of ‘Marselan’ grape was determined by combining physical and chemical indexes, polyphenol indexes and sensory evaluation of wine.The results showed that the reducing sugar content continued to increase and the titrable acid content gradually decreased after the color transformation, and the change range was small near the harvest period.The contents of total phenols, anthocyanins and tannins in fruit peel increased first and then decreased, but the changes of total phenols and tannins in fruit seeds were different from those in skin and showed a fluctuating trend.According to the technical maturity index（sugar-acid ratio）,the ‘Marselan’ grape in Zhangye area had reached the conditions of harvesting on September 1^st,meeting the raw material requirements for making dry red wine.Considering the quality of grape raw materials and wine quality, it was most suitable to harvest and make ‘Marselan’ grapes in Zhangye area on the 5 day around September 22^th,when the sugar content of raw materials was ＞270 g·L^-1 and the sugar-acid ratio was ＞32,which meet the requirements of making high-quality dry red wine.