Abstract: This study was conducted to determine the effects of diets without L-lysine on internal organs and serum biochemical parameters for piglets. 21 three-way cross piglets were weaned at the age of 28 d and the bodyweight of about 6.53±0.39 kg,then they were randomly divided into three groups and fed zein diets (diets lacked lysine), zein diets supplemented with L-lysine and N-free diets respectively, the experiment lasted for 21 days. The effects of diets without L-lysine on internal organs and serum biochemical parameter were observed. Different test diets did not cause any significant (P >0.05) change in the internal organ index of weaned piglets. Serum concentration of AST, LDH, CK, LDL, GLU had significant (P <0.05) differences among different test diets. Serum concentration of AST, LDH, LDL in N-free diets group were increased significantly (P <0.05), the numbers were 81.73 ?滋/L, 600.36 ?滋/L and 2122.35 mmol/L respectively, while serum CK in zein+lysine group was the highest, 694.89 ?滋/L, and the serum GLU was the lowest, 3.40 mmol/L, among the three groups. Serum IgM, UREA in different diet groups showed extremely significant difference (P <0.01). Daily diets lack of lysine could affect blood related enzyme (AST, LDH and CK) activity to some extent, which lead to anti-stress ability decreased. A piglet diet lack of lysine also affected immune index (IgG、LDL), resulting in a decline in resistance. At the same time, the blood sugar and serum urea nitrogen level were also influenced, caused blood sugar increase, nitrogen use efficiency was reduced, but did not affect the internal organs index.