In order to accurately evaluate the harvest maturity of blueberries and ensure fruit quality, the experiment selected six blueberry cultivars: ‘Northland’, ‘Bluecrop’, ‘Draper’, ‘Reka’, ‘Duke’, and ‘Blue gold’ as test materials, and used near-infrared spectroscopy to establish regression model to determine the relationship between soluble solids, titratable acids, hardness, anthocyanins, vitamin C, and absorbance difference index (IAD value). Research had found that with fruit maturity increase, the titratable acid and hardness of blueberries significantly decreased, while the contents of soluble solids, vitamin C, and anthocyanins generally showed an upward trend. The IAD value of blueberries showed a highly significant positive correlation with anthocyanins (r=0.90, p≤0.01) and a significant negative correlation with hardness (r=-0.82, p≤0.01). Additionally, there was a positive correlation with vitamin C and soluble solids, and a negative correlation with titratable acid. Regression equations were derived to describe the changes in the IAD value based on the five quality indicators, demonstrating that the IAD value can reflect the fruit maturity. The recommended harvest standards for the six main cultivars are as follows. The IAD values of ‘Northland’ and ‘Lanjin’ are 1.9-2.0, the IAD values of ‘Bluecrop’ and ‘Draper’ are approximately 1.8, and the IAD values of ‘Reka’ and ‘Duke’ are 1.7-1.8.