In order to study on requirement on nitrogen, phosphorus and potassium by tea plants with different ages under field conditions, the biomass on up-ground parts of Longjing 43 tea plants aged 1, 2, 3, 5 and 10 years in the fall of the first year, and the young shoots, the fallen leaves and the pruning on the second year under different N, P and K application was investigated. The biomass of up-ground parts in tea plants aged 5 years and the concentration of N, P and K in tea plants increased 32, 21, 25, 29 times respectively as compared with those aged one year. The biomass and the concentration of N, P and K in tea plants aged 10 years only increased approximately by 71%, 17%, 13%, 14% respectively as compared with those aged 5 years. The annual requirement of N, P and K for tea plants aged 1~2 years under field conditions is 90.01, 5.71, 31.11 kg/hm² respectively. The annual requirement of N, P and K for tea plants aged 2~3 years is 122.74, 9.63, 45.14 kg/hm² respectively. The annual requirement of N, P and K for tea plants aged 3~4 years is 144.03, 10.33, 47.99 kg/hm² respectively. After pruning, the absorbed N, P and K in part is recovered to the soil through pruning and fallen leaves, the amounts of N, P and K in tea plants used for growth (pruning and fallen leaves are excluded) account for 43.9%, 48.7%, 61.3% of the total respectively. The annual requirement of N, P and K of young tea plants (for example, 5 years aged tea plants) is about 164.4, 12.68, 71.29 kg/hm² respectively. The concentration of N, P and K in the plucking tea plants is mainly used in the growth of tea shoots, and maintain in a stable state and only share a small part of the total (approximately 7.54, 0.53 and 5.44 kg/hm²). A research method on the requirement on N, P and K of tea plants with various growing stage under field conditions was established in this investigation, thus provides a new idea for the further investigation on the nutrient requirement of tea plants.