Abstract: The essence of crop production is a complex system that is driven by light energy. The accumulation of 90% of the dry matter comes from the production of photosynthesis. In this study, we investigated the effect of Eucalyptus grandis leaf litter decomposition on the growth and photosynthetic characteristics of Eremochola ophiuroides. Four treatments with different amounts of leaf litter were designed, including T1 (30 g/pot), T2 (60 g/pot), T3 (90 g/pot) and control (0 g/pot, CK), and the blank experiment groups with distilled fallen leaves were set as the above. The growth indexes were measured at 30, 60 and 90 d after sowing, and the photosynthetic characteristics were tested on the mature leaf in the middle of stolon. The test results showed that increasing amounts of E. grandis leaf litter significantly inhibited the accumulation of biomass, growth, synthesis of photosynthetic pigments of E. ophiuroides seedlings (P<0.05). Meanwhile, the stomatal conductance and the adaptation capacity to the change of light and CO₂ in the environment of CK were significantly lower than which of treatments. This demonstrated that the allelochemicals from E. grandis leaf litter decomposition can negatively affect the photosynthetic capacity and decrease the accumulation of biomass, and eventually inhibit the growth of E. ophiuroides.