In recent years, peptide drugs, with their abundant targets, high activity and specificity, and minimal adverse effects, have gained increased attention. This chapter focuses on peptide drugs’ characteristics and pharmacokinetic research strategies from the perspective of the DMPK. It delves into the metabolic characteristics and optimization strategies to enhance peptide stability and bioavailability. Insights into absorption, distribution, metabolism, and excretion (ADME) studies of 37 approved therapeutic peptides are presented, spotlighting their radiolabeling considerations and strategies. This chapter also addresses the challenges and strategies in the bioanalysis of peptide drugs.