In this experiment, the biochemical components of 18 white tea samples with different grades, three-year-aging and compressed treatments or not from Fujian Province were tested and compared. At the same time, the umami, bitterness and astringency of white tea samples were graded by the method of taste equivalent quantification evaluation. Based on the above results, correlation analysis, principal component analysis and multiple linear regression analysis were used to screen the main biochemical components related to each taste; furthermore, evaluation models were established. The results showed that the average amount of tea polyphenols and amino acids in Baihaoyinzhen (BHYZ) samples were 20.14% and 5.42%, respectively. With the decrease of white tea grade, the contents of tea polyphenols, ester catechin and gallic acid decreased, while the flavone content increased. Amino acids and caffeine contents were similar in BHYZ and Baimudan (BMD), but significantly higher than those in Shoumei (SM) white tea. In aged white tea, the contents of amino acids, soluble sugar, tea polyphenols, ester catechin and gallic acid in compressed aged white tea were lower than those in loose aged white tea. For quantitative evaluation of the umami, BHYZ got the highest score, and BMD had the higher scores in umami, astringency and bitterness. For SM, all taste scores were the lowest. The umami and astringency scores of aged white tea were lower than those of new white tea, and the umami score of the compressed aged white teas further declined. Overall, this study provides consumers with a scientific method to understand the quality of white tea, enriches the biochemical theory for white tea, and provides a theoretical basis for the promotion of white tea.