Abstract: A field experiment was conducted to study the effects of foliar spraying three compound agents ［plant polysaccharides (P₁), plant polysaccharides and 5-aminolevulinic acid (P₂), and plant polysaccharides and 5-aminolevulinic acid and dimethylpiperidinium chloride (P₃)］ at the initial flowering stage of soybean on its leaf chlorophyll content, photosynthesis and transpiration, dry matter accumulation and allocation, and grain yield. Within 35 days after spraying the three compound agents, the leaf chlorophyll content had obvious increase, and its decreasing trend with plant growth had somewhat delay. Compared with the control, spraying P₁ and P₃ increased the leaf photosynthetic rate and water use efficiency by more than 13.2% and 10.3%, respectively. With the spraying of the three compound agents, the dry matter accumulation in aerial part increased, and the allocation of dry matter from leaf to pod was also enhanced, with the contribution of postanthesis assimilates to grain yield increased by more than 17.1%. The 100-grain mass and the pods and seeds per plant increased significantly after spraying P₁ and P₃, but had no significant increase after spraying P₂. The grain yield of soybean treated with the three compound agents increased by more than 5.9%, compared with the control. This study showed that the three plant polysaccharide compound agents could increase the leaf chlorophyll content, delay the leaf-senescence, improve the leaf photosynthetic capacity and water status, effectively control the dry matter accumulation and post-anthesis assimilates allocation, and increase the grain yield of soybean.