The invention relates to the technical field of nano agriculture, and particularly discloses application of a copper nano-fertilizer to improvement of tomato resistance and yield. The copper nano-fertilizer is a zero-valent Cu nano-material, and the size of the copper nano-fertilizer is 1-10 nm. According to the invention, the tomato resistance can be remarkably improved, aging of tomato leaves is slowed down, photosynthesis is enhanced, root growth and nutrient absorption are promoted, and the tomato yield is increased. Meanwhile, Cu is not enriched in tomato fruits. The Cu-based nano-fertilizer disclosed by the invention has the advantages of greenness and biological safety when being applied to tomato planting.