<p>In forensic practice, accurately estimating post-mortem interval (PMI) is a crucially significant task, as it can provide key clues for cases in forensic medicine. However, it has also been a major challenge since ancient times. Currently, the traditional methods used in forensic medicine to infer PMI mainly include early post-mortem phenomena, corneal opacity, degree of gastric content digestion, and entomological analysis, but are significantly influenced by environmental factors and individual differences, presenting certain defects in terms of precision and applicability. With the advancement of modern molecular biology techniques, the application of gene expression analysis in the area of forensic medicine has gradually become a research hotspot. Moreover, the integration of machine learning algorithms and artificial intelligence (AI) can analyze multi-source data to construct prediction models, thereby improving the correctness of PMI inference and expanding its application scenarios. In this review, we elaborate on the research advancements, mainly in molecular biology or forensic molecular genetics of PMI estimation in forensic medicine. By systematically reviewing the latest research findings of molecular biology in PMI estimation and exploring its future directions, this review also endeavors to offer valuable references for forensic practitioners to improve the reliability of PMI inference in practical forensic potential applications in the future.</p>