This paper focuses on the pharmacokinetics in fattening pigs as well as the change of serum resulting from the use of porcine somatotropin(PST) and its liposomes. A slow-release model was determined to be relevant to following an examination of all dynamic parameters. The results indicate that the slow-release effect of PST liposomes was significant, with an extended release time of over 7 d. This paper focuses on the pharmacokinetics in fattening pigs as well as the change of serum resulting from the use of porcine somatotropin (PST) and its liposomes. A slow-release model was determined to be relevant to following an examination of all dynamic parameters. results indicate that the slow-release effect of PST liposomes was significant, with an extended release time of over 7 d.