This article deals with the influence of tea plantation on the acidification of yellow-brown earth. The soil pH decreased after planting tea, and the soil tended to be further acidified with the time of growing tea. The decrement of soil pH was higher in upper layers,than in lower layers. The acidification of soil in tea garaen was related to the biological accumulation of aluminium and fluorine by tea trees, to The increade of soil exchangeable aluminium and aluminium complexes, and to the eluviation of basic canons in soils. The contents of aluminium and fluorine in the fallen leaves of tea were 5836-6136 ppm and 469-520 ppm respectively, and the aluminium content in the percolating solution of soil in tea garden decreaed from 0.46-0.55 mg L^-1 in the litter floor to 0.01-0.15 mg L^-1 in the 50 cm deep soil. Aluminium and fluorine cycle in tea garden resulted in not only the increase of Al³⁺ and F^-1 in soil bur also the accumulation of organic complex aluminium in surface soil and aluminium-fluorine complexes in soil exchangeable complexes and soil solution. Therefore, the accumulation of aluminium and fluorine in soils and its hiogeochemical cycle were the main reason fof the acidification of soils in tea gardens.