Abstract: Investigation on the main factors that affect the quality of wine grape Merlot， could be used to improve the grape breeding and selection， and to provide the theoretical basis of wine grape industry upgrade in Hexi region. The nine evaluation indexes of the grape quality in Hexi region were analyzed and optimized with the fuzzy system analysis， so as to reveal the main factors which affected the Merlot grape quality， and its quality was graded in Hexi Region. The results showed that the main factors which affected the Merlot grape quality in Hexi region were titratable acid，phenol， tannins， anthocyanin， total sugar and soluble solids. Moreover， the nine evaluation index of the grape quality were optimized. According to the evaluation index vector， the result showed that more than 90% of Merlot grape quality was better than the second class in Hexi region. Thus， the six indexes of titratable acid，phenol， tannins， anthocyanin， total sugar， soluble solids can be used as the simple indicators to evaluate the quality of Merlot grape.

Key words: fuzzy system analysis, Merlot grape, Hexi region, quality evaluation