Abstract: In order to improve the reproductive efficiency of pink heelsplitter, Potamilus alatus, and explore the influence of parasitism on nutritive index of freshwater drum, Aplodinotus grunniens, this experiment measured the effect of parasitism of different scales through comparing the amount of glochidium falling from freshwater drum, and analyzed changes of serum biochemical indices of the host, and content of amino acid and fatty acid under stress of parasitism. Results indicated that the amount of glochidium falling from the hosts in group of big freshwater drum is significantly greater than that in group of small freshwater drum (P<0.05), while the average amount of juvenile mollusk falling from the hosts in each kilogram in group of small freshwater drum is much bigger than that in group of big freshwater drum (P<0.05); creatinine in muscles significantly increases under stress of parasitism (P<0.05), and glutamic-pyruvic transaminase, glutamic oxalacetic transaminase and lactic dehydrogenase greatly drop (P<0.05), while blood glucose, total protein, albumin, triglyceride, total cholesterol, high-density lipoprotein and low density lipoprotein barely change comparing with those in the control group (P>0.05); ash content in the experimental group barely differs from that in the control group (P>0.05), and water content and crude fat in muscle in the experimental group are significantly higher than those in the control group (P<0.05), while content of crude protein in experimental group is obviously lower than that in the control group (P<0.05); content of aspartic acid, alanine, glutamic acid, tyrosine, glycine and arginine in the experimental group are greatly lower than those in the control group (P<0.05), and content of non-essential amino acid is notably lower than that in the control group (P<0.05), while the content of other amino acids in two groups are barely different (P>0.05); the content of lauric acid (C12:0) and arachidonic acid (C20:1) in the experimental group are remarkably higher than those in the control group (P<0.05), while there is no other significant difference (P>0.05). Results indicated that small size host fish is more suitable for practical production and parasitism had little influence on the nutritive index of freshwater drum.