ObjectiveTo understand the progress of molecular biology research on the pathogenesis of hemorrhoids. MethodThe literatures relevant to reseaches on the molecular biology of hemorrhoid pathogenesis in recent years had been reviewed. ResultsThe generally accepted theories of hemorrhoids included anal cushion downward movement theory, varicose vein theory, and vascular proliferation theory. The molecular biological studies related to the theory of anal cushion downward movement found that the increased expression of matrix metalloproteinase-9 and the abnormal expression of smooth muscle actin could damage the supporting tissue of anal cushion, causing the downward movement and prolapse of anal cushion, and then formed hemorrhoids; The molecular biology researches related to varicose vein theory found that the increase of nitric oxide synthase and transient receptor potential vanilloid 1 could promote the production of nitric oxide, causing varicose veins, and then leaded to the pathogenesis of hemorrhoids; The molecular biology researches related to vascular proliferation theory found that the low expressions of miR-412-5p and miR-4729, and the overexpressions of vascular endothelial growth factor and fibroblast growth factor were related to the vascular proliferation of hemorrhoids. In addition, the secondary inflammatory reaction after the onset of hemorrhoids also played an important role in the occurrence and development of hemorrhoids. ConclusionsThe occurrence and development of hemorrhoids is the result of the intersection and interaction of various mechanisms such as anal cushion downward movement, varicose veins, vascular proliferation, and secondary inflammatory reaction. The molecular biology research on the pathogenesis of hemorrhoids is helpful to better explain the occurrence of hemorrhoids from a microcosmic perspective, and lay a foundation for further exploring the etiology of hemorrhoids.