Abstract: The mechanism of TiO₂ semiconductor photocatalysis had similarity with artificial photosynthesis. The effects of nano-TiO₂ photosemiconductor sol on the photosynthesis of cucumber plants had been firstly reported in this paper. Anatase TiO₂ semiconductor used in the experiment was synthesized by sol-gel methods, and its effects on photosynthesis, activities of root systems and contents of leaf cell malondialdehyde had been studies after spray different concentration of nano-TiO₂ sol on cucumber leaves in culturing experiments. The experimental results showed that nano-TiO₂ sol could form perfectly adhesive, transparent, continuing and stable films on the surfaces of leaves by which net photosynthetic rates and activities of root system had been significantly promoted. These results provided some scientific and technical references for application of nanomaterials which using TiO₂ as effective ingredients in agricultural research.