As a non-invasive drug delivery system, transdermal drug delivery systems (TDDS) have many advantages over traditional injection and oral administration, and are very suitable for diseases that require frequent or long-term treatment. Based on the research progress of transdermal drug delivery systems in recent years, this article summarizes and reviews the mechanisms of transdermal drug delivery, factors affecting drug penetration through the skin, as well as methods to promote drug transdermal absorption, and prospects the future development trend of transdermal drug delivery system.