Abstract: In this paper we have studied the effect of different light intensities on some photosynthetic properties of Setaria italica and Arachis hypogaea after shading treatment. The effects are expressed as follws The light compensation and saturation point of both crops are descended; Under lower light intensity, the rate of apparent photosynthesis and initial slope of light-photosynthetic curve are ascended; Especially, the rate of relative photosynthesis increases distinctly. Simultaneously, the chlorophyll and water content of the leaves are increased. The thickness of leaves becomes to be thin and the photosynthetic production decreased. The varying tendency of these characteristics is identical, but different on its extent. On the other hand, their apparent photosynthetic rates under the condition of light saturation, as the response to shading treatment, are quite different. Setaria italica is descended, while Arachis hypogaea is almost stable. According to the photosynthetic properties of these crops, it is clear that Setaria italica is a suny plant while Arachis hypogaea borderes on shade tolerant one. The shade tolerance of Arachis hypogaea is higher than that of setaria italica. Some data in this paper may provide a reference to arrange the structure of intercropping communities consisted by Setaria italica, Arachis hypogaea and some crops with tall stem, such as corn or sorghum.