Abstract: Three fungicides (25% AONING, 70% Mancozeb, 55% sodiump (dimethylamino) benzenediazo sulfonate) toxicity on cucumber root rot were tested by hypha growth speed of Northern Shaanxi and Guanzhong region solar greenhouse, carry out fungicides treatment soil and irrigate root experiment .The result showed that three fungicides have obviously repress function on hypha growth in two pathogens. The best effect was 25% AONING WP, the followed was 55% sodiump (dimethylamino) benzenediazosulfonate WP, the worst is 70% Mancozeb WP. Guanzhong Region Pathogens EC50 separately was 0.3754, 219.5887, 105.5966. Northern Shaanxi Pathogens EC50 separately were 0.2771, 160.5462, 89.5241. Economics effective amount used in the field is 200g, 2000g, 2000g. The result of irrigate root are not remarkable, and not suitable promoted in the production.