Abstract： Objective： Benign prostatic hyperplasia is a benign chronic disease that causes urination disorder in middle-aged and elderly men. Studies have found that hyperplasia of interstitial components and enlargement of the gland are the main pathological changes. The “collateral disease theory” believes that this disease is pathologically featured by easy deficiency and stasis， easy to form by accumulation， and prolonged diseases transforming to collaterals； the root of pathogenesis is emptiness and deficiency of kidney collaterals，the obstruction of collaterals is the mechanism，and the damp-heat，blood stasis and turbidity is the branch. Among them， the obstruction of collaterals is the core pathogenesis of benign prostatic hyperplasia； the principle of treatment is to unblock， and the methods of freeing the collateral vessels by supplementing deficiency，activating blood and eliminating the pathogenic factors are often used to treat benign prostatic hyperplasia. On the basis of “collateral disease theory”，the author combined with modern medical research to explore the etiology， pathogenesis and treatment of benign prostatic hyperplasia to provide new ideas for the staging treatment of the disease with traditional Chinese medicine.