Effects of applied boron (soil application of boron,spraying boron on the plant) on the boron forms and leaf photosynthesis of papaya plants were investigated.The results showed that the two methods of boron application both increased the contents of boron forms and the total content of boron in plant leaves,petiole and root,in which the water soluble boron,semi-bound boron and total content of boron in leaves increased significantly.The increase of boron content of plants increased photosynthetic rate in leaves,but excessively high level of boron could inhibit the photosynthetic capacity,and even lead to a significant drop of photosynthesis.