Objective To study the difference of blood amino acids and acyl carnitine between full-term small for gestational age newborns and their matched full-term suitable for gestational age newborns, so as to provide reference for the supplementation of amino acids in full-term small for gestational age newborns. Methods From April 2019 to July 2020, a total of 57 cases of full-term small for gestational age newborns in Hunan Provincial Maternal and Child Health Hospital were selected into study group, and meanwhile 57 cases of matched full-term suitable for gestational age newborns born in this hospital were selected as the control group.The levels of blood amino acids and acyl carnitine between the two groups were measured respectively, and their differences were analyzed. Results There were no significant differences in butyryl carnitine, 3-hydroxy isoamyl carnitine, isoamyl carnitine, sunoyl carnitine, leucine and methionine between study group and control group (t=1.707, 1.122, 1.122, 1.638, 1.855, 1.638, P>0.05), but significant differences existed in propionyl carnitine, free carnitine, myristoyl carnitine, octanoyl carnitine, tyramine and valine between the two groups (t=5.524, 3.392, 4.530, 4.716, 4.530, 3.547, P<0.05). Conclusions There are significant differences in blood amino acids and acyl carnitine between full-term small for gestational age newborns and full-term suitable for gestational age newborns, so full-term small for gestational age newborns are given critical attention from clinicians.It is supposed to supplement amino acids for full-term small for gestational age newborns as soon as possible, and to encourage early mobilization of medium and long chain fatty acids to stabilize energy metabolism.