In this study, the profile amino acids of body composition of Penaeus semisulcatus were primarily determined. Then on that basis, three nearly isocaloric (386.5, 376 & 373.5 Kcal/100gr) diets with dietary protein contents of 40%, 45%, 50% were prepared. Chineh feed (commercial grow-out feed in Iran) was also used as control diet.Each diet was fed in two replicate tanks three times a day. Juvenile shrimps with and average size of 1.9 gr were reared for 60 days, a direct relationship was observed between dietary protein content and growth performances. For P. semisulcatus, diet containing 45% protein had food conversion ratio (FCR), profit and protein deposition higher than others. Diet containing 50% protein had specific growth rate (SGR), yield, weight gain per day, final mean length &weight higher than others. As the blank diet had been made for P. indicus, it was not practically suitable for this shrimp. Optimal diet protein for this species was diet with 45% protein.Applying the Broken Line response method with SGR data was established the same 45% protein.