This　study　was　conducted　to　investigate　the　efficiency　of　TiO2　photocatalytic　nanomaterial　as　a　novel　environment-friendly　disinfectant　to　control　plant　fungal　diseases　(Sphaerothecaf　uliginea)　by　its　photochemical　sterilization　ability　in　cucumber　plants.　Anatase　nano-TiO2　sol,　a　neutral,　viscous　aqueous　colloid　of　1.4%　TiO2,　was　synthesized　by　sol-gel　method.　Control　efficiencies　of　nano-TiO2　sol　in　preventing　from　powdery　mildew　were　measured　by　field　experimental　method　with　cucumber　seedling　naturally　infected　Sphaerothecaf　uliginea.　Results　showed　that　spraying　certain　content　of　nano-TiO2　sol　could　form　continuous　and　stable　antibacterial　films　on　blade　surfaces　which　could　not　only　significantly　reduce　lesion　areas,　disease　incidences　and　disease　indexes　of　powdery　mildew　but　also　make　the　leaves　turn　much　greener.　It　was　initially　confirmed　that　nano-TiO2　sol　could　effectively　delay　and　inhibit　the　development　and　pervasion　of　cucumber　powdery　mildew.　These　results　indicate　that　nano-TiO2　sol　can　be　developed　as　environment-friendly　fungicide　in　preventing　from　plant　disease　developments.　©　(2013)　Trans　Tech　Publications,　Switzerland.