Body composition,growth,faecal production,nitrogenous excretion and nitrogen budget of juvenile mandarin fish ［Siniperca chuatsi (Basilewsky)］ (initial body weight 2.52-3.79 g,average 3.11 g) at different ration levels (starvation,1%,2%,3%,4% of initial body weight per day,and satiation) were investigated in this study.The relationships between growth,nitrogenous excretion,faecal production and ration were studied and the regression equations were established.Water temperature was controlled between 26.5℃ and 28.0℃,and the average level was 27.3℃.The results showed that with the ration level increasing,the contents of dry matter,protein and lipid increased,but ash content decreased.With the increasing of ration level,feed conversion efficiency (FCE,%) tended to increase,feed absorption efficiency (FAE,%) tended to increase within a narrow range and specific growth rate increased with a linear pattern.Excretion nitrogen [UN,mg/(g·d)] and faecal nitrogen [FN,mg/(g·d)] increased markedly with increased ration level (LR,% per day),with the regression equations of UN=0.449 6LR+0.097 9 and FN=0.078 1LR+0.019 2,respectively.With the ration level increasing,allocation of nitrogen to growth increased,proportions of excretion nitrogen and faecal nitrogen decreased,and the nitrogen budget of juvenile mandarin fish at satiation was:100CN=45.20GN+7.46FN+47.34UN.