Abstract: In order to discover highly effective fungicides against Corynespora cassiicola on cucumber, the inhibitory activities of 19 fungicides against mycelial growth, spore germination and germ tube elongation of C. cassiicola were measured. The effects of the 4 selected effective fungicides on mycelial and conidial morphology were also evaluated. The results showed that fluazinam, isopyrazam, fludioxonil and tetramycin exhibited strong inhibitory activities against mycelial growth, spore germination and germ tube elongation at each growth stage of C. cassiicola. The average EC₅₀ value of the four fungicides for inhibiting mycelial growth were 0.516 3, 1.538, 1.605 and 0.648 2 mg/L, respectively. The average EC₅₀ value of inhibiting the spore germination were 0.164 4, 1.359, 1.127 and 0.002 5 mg/L, respectively. The average EC₅₀ value of inhibiting germ tube elongation were 0.189 6, 0.144 7, 0.060 4 and 0.001 5 mg/L, respectively. Fungicides with different modes of action, such as boscalid, chlorothalonil and trifloxystrobin, showed high efficacy against spore germination and tube elongation of C. cassiicola. The average EC₅₀ value of three fungicides to inhibit the spore germination were 1.564, 0.373 0 and 0.021 3 mg/L, respectively. The average EC₅₀ value of inhibiting the germ tube elongation were 0.629 5, 0.233 4 and 0.405 0 mg/L, respectively. But the inhibitory activities against mycelial growth were poor, the average EC₅₀ value were greater than 16 mg/L. After the treatment of fluazinam, isopyrazam, fludioxonil or tetramycin, the morphology of mycelial and conidia was studied. The microscopical observation showed that the mycelial septa spacing decreased, the edge of diaphragm appeared as intumescent and two branches of the main mycelia frequently occurred. In addition, mycelia became distorted and adhesive, the new branches of mycelium were inhibited or conidial growth was metamorphotic. Given that fluazinam, isopyrazam, fludioxonil and tetramycin showed excellent inhibitory virulence against C. cassiicola, these fungicides are potential candidates for the control of C. cassiicola in the field.