The present application relates to a method for defoliating hemp, a defoliant and application thereof. The method for defoliating hemp according to the present application comprises applying 2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine before harvesting hemp, the amount of application of 2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine being 20-450 g of active substances per mu, preferably 90 g of active substances per mu. The method according to the present application has the advantages of high efficiency, low toxicity, no impairment to the quality of hemp fiber, small amount of application, and economical and practical properties.