Feeding experiments were conducted with protein diets ( PD) and protein..free diets ( FPD) for juvenile Penaeus vannamei ( average body weight s, 0. 2627- 0. 2715g ) . The diets( PD) are prepared by casein and gelat in as protein source with high biological values. The requirements of juvenile Penaeus vannamei for essential amino acids ( EAA) were determined based on the daily depo sition and changes of each EAA in shrimp body. The minimum requirements of EAA needed to satisfy the requirements of juvenile Penaeus vannamei growth ( g- 1..( 100g body weight) - 1..d- 1) were Threonine 0. 046, Valine 0. 054, Methionine 0. 029, Isoleuline 0. 069; Leucine 0. 087, Phenylalanine 0. 051, Lysine 0. 086, Histidine 0. 025, Arginine 0. 097. When dietary protein levels was 40%, net protein ut ilization ratio was 50% and the feeding rate was 20% of the body weight, the minimum contents of EAA in the dietary ( g ..kg - 1 diet ) were as follow s, Threonine 11. 5, Valine 13. 5, Methionine 7. 3, Isoleuline 17. 3, Leucine 21. 8; Phenylalanine 12. 8, Lysine 21. 5, Histidine 6. 3 and Arginine 24. 3.