Abstract: Changes of biochemical composition of black tea,Dangui,in processing were investigated.The results indicated that(a) the water extract and tea polyphenols in Dangui decreased gradually;(b) the amino acids content increased in the beginning,but decreased in the later stage;(c) the ratio of polyphenols to amino acid decreased;(d) the contents of TFs,TRs and TB as well as the total amount of the three tea pigments increased gradually;(e) the total catechins content in the finished black tea decreased considerably,only 1/10 of what was in the fresh leaves;and(f) the individual catechins also decreased,with the greatest reduction on epigallocatechine gallate followed by epigallocatechine,gallocatechine gallate,epicatechine gallate,epicatechine and D,L-catechine.Sensory evaluation showed that the beverage steeped from Dangui black tea had a strong sweet note,attractive reddish color,a mellow but flavorful aroma and excellent general quality.