This review systematically summarizes research progress in the evaluation of the effectiveness and safety of the transdermal absorption of cosmetics, focusing on the classification, applicability, and relevant regulations of different evaluation methods. Transdermal absorption refers to the process in which active ingredients enter the epidermis, dermis, and other parts of the skin through the skin barrier and exert their effects. The article first classifies the in vitro and in vivo evaluation methods of transdermal absorption. It also provides a detailed overview of the regulations and standards for in vitro transdermal absorption, compares the standards of different institutions, and highlights the diffusion cell method, developed by scientists at Procter & Gamble, which is the mainstream method for in vitro testing. In addition, the paper summarizes the utilization of modern testing techniques such as high-throughput screening technology, mass spectrometry imaging, Raman spectroscopy, and confocal microscopy in the study of transdermal absorption and introduces the working principles of various instruments and their specific application cases in transdermal absorption studies.