The carbon budget of Chinese Prawn(Penaeus chinensis)fed with polychaete worm (Neanthes japonnica) under different salinity and fed with different diets (polychaete worm and formulated diet)under salinity of 31 was studied .The experimental results showed that the salinity ranging from 5 -35 and the temperature at 25 ℃, the maximum carbon intake was 61 .64(mg·g -1· d -1)at salinity of 13 , but the suitable salinty for growth is 20 , and carbon conversion efficiency was highest of 25 .84 %, the best specific growth rate from carbon is 3 .89 %.The mechanism of salinity effect on carbon growth of the prawn was decided by food intake and carbon conversion efficiency .The growth of Chinese prawn fed with polychaete worm was significantly larger than that fed with formulated diet .Their carbon conversion efficiency was 26 .80 % and 13 .78 % of carbon intake respectively .The mechanism of food effect on carbon growth was decided by assimilation ratio and conversion efficiency .