The invention discloses a botanical mosquito larva killing agent containing effective components of Carduus crispus L.. The prepared botanical mosquito larva killing agent containing the effective components of Carduus crispus L. is prepared through treating fine Carduus crispus L. strain powder or Carduus crispus L. extractsas a main effective component and adding assistants, and can be a soluble liquid, a wettable pulvis, a water dispersible granule, a particulate agent, a microemulsion or an emulsion in water. The botanical mosquito larva killing agent has the advantages of substantial larva killing effect, low toxicity, low residual, difficult generation of pests' resistances to the larva killing agent, simple preparation technology, and low cost, accords with present pesticide development trends, and can be applied to indoor and outdoor mosquito growth places, and sensitive areas such as drinking water processing areas and the like.