Abstract: With Jiefangzhong loquat as material, the correlation between flavonol synthetase (FLS) genetic expression and flavonol accumulation during fruit development was analyzed in this paper, and then the molecular mechanism of flavonol accumulation in loquat fruits was discussed. High Performance Liquid (HPLC) was used to determine the content of flavonol in loquat fruits at different stages, and the expression level of FLS gene in fruits at different development stages was detected by using RT-PCR. The results showed that the content of flavonol was the highest in loquat fruits, followed by that of flavanonol. And the content of flavonol has tended to decrease on the whole in the ripening process, which was reducing greatly especially in the early stage of fruit development (55-65 d after anthesis). However, the content of flavanonol was on the rise, and the change trend of the expression level of FLS gene was similar to that of flavanol. The expression level of FLS gene in loquat fruits at different stages had significant positive correlation with the content of flavonol, while it had significant negative correlation with the content of flavanonol, indicating that FLS gene had a significant positive regulating effect on the synthesis of flavonol in loquat fruits.