Cynanchun komarovii extract and its application

The present invention relates to a crude extract of Cynanchum komarovii Al.Iljinski and its activity for resisting plant virus. The active component resisting virus of tobacco mosaic disease in the ethyl alcohol extract of above-ground portion of the Cynanchum komarovii Al.Iljinski is phenanthronidolizidine alkaloid, in which 7-demethoxytylophorine (antofine) is its main active component. As compared with existent extensively-used preparation for resisting tobacco mosaic disease, its activity can be raised by 1-2 orders of magnitude. Said invention can be extensively used for controlling viral disease of plant.