：By using the material of de-catechined tea extracts in tea comprehensive processing and on the basis of selecting the best pH value of liquid for separation and concentration theanine by ultra-filtration,the effect on the yield rate and purity of theanine by 2500βDa、3500βDa、5000βDa ultra-filtration and four concentrating method of 300βDa nano-filtration、200βDa nano-filtration、reverse osmosis、vacuum vaporation concentration were comparatively studied in processing the de-catechined tea extracts. The results indicated that it was beneficial to separate and concentrate theanine from de-catechined tea extracts when the value of pH was 2.8~3.5.3500βDa ultrafiltration had a good effect in separating and concentrating theanine ,the major tea polyphenol ,water soluble carbohydrate were preserved and the cut rate reached 89.90%、92.20% respectively, the yield rate and purity of theanine was 54.50%,8.92% respectuvely. The lost rate of theanine in concentrating of 300βDa nano-filtration、200βDa nano-filtration、reverse osmosis、vacuum vaporation concentration was 4.51%、3.62%、0.45%、5.15% respectively. Take all thing into account, it is feasible to separate and concentrate theanine from de-catechined tea extracts in tea comprehensive processing industry by the joint application of ultra-filtration and reverse osmosis,and the yield rate and purity of theanine can reach 54.05% and 8.53% respectively.