Abstract: We compared and analyzed the nutritive components and amino acid composition of peanut worm (Sipunculus nudus)at larval, juvenile and adult stages. The crude protein contentsat those 3 stages were 56.46%, 66.40% and 74.84%, respectively; the crude lipid contents were 2.51%, 2.65% and 2.95%, respectively; the crude ash contents were 30.89%, 18.88% and 7.86%, respectively; the total sugar contents were 8.35%, 5.81% and 5.62%, respectivley; the moisture contents were 93.54%, 89.04% and 85.95%, respectively. With the growth of S.nudus, the contents of crude protein and lipidincreased gradually, whilethose of crude ash, total sugar and moisture decreased. Thecontents of most amino acids increased significantly. The contents of Glycine (Gly) and Histidine (His)at the 3 stages were 2.90%, 6.94%, 5.57% and 1.15%, 1.51% ,1.48%, respectively; they increased significantly in larval and juvenile stages (P0.05);at adult stage, the contents of Gly decreased significantly (P0.05) while that of His remained relatively stable. The EAA/TAA ratesat the 3 stages were 31.98%, 27.56% and 32.61%, respectively, whose difference is significant (P0.05). The DAA/TAA rate at larval stage was the highest(58.76%), but there is no significant difference between juvenile and adult stages (P0.05).