Abstract:Colletotrichum lagenarium can induce resistance in cucumber against brown-spot. The effect of resistance can reach 97.83% if the cucumber inoculated by Colletotrichum lagenarium (1.0×106 spores/mL) 48hours. The ability of challenge is different, Colletotrichum lagenarium is stronger and absorbed more in the same grade on nutrition. The accumulation of callose in leaves of induced cucumber increased obviously by toluidine blue. Also, results of study of mechanism show that the way of infection is different between Colletotrichum lagenarium and Corynespora cassiicola after stained. The invasion of former is through stoma or attack cell wall, directly, but the latter by cell wall only.