A pea-derived peptide with a muscle-building effect and a preparation method thereof, and a drug and use, are disclosed. A pea protein is subjected to enzymatic hydrolysis, and five polypeptides with muscle-building effect are obtained by separation as separate peptide fragments. In an in vitro aging skeletal muscle cell assay, changes are analyzed in a gene expression level of regulatory pathways related to skeletal muscle cell proliferation and differentiation, apoptosis and autophagy, and protein synthesis and degradation. In addition, animal experiments are conducted to study the muscle-building effect and a corresponding mechanism of the pea-derived peptide. This shows that the five polypeptide sequences have a significant muscle-building effect, usable as a polypeptide drug for the treatment of sarcopenia.