Abstract: Effects of Cd²⁺ on biomass of Lolium perenne were studied, and Cd accumulative characteristics were also elaborated. L. perenne were treated with Cd²⁺(0, 5, 10, 20 mg/L) for 6 days. The biomass of aboveground and underground decreased significantly . With the Cd²⁺ concentration increasing, the Cd content in L. perenne increased significantly, and the distribution proportion of Cd in underground decreased significantly, contrary in the aboveground. L. perenne had the excessive ability in absorbing and transporting Cd. In order to explore the photosynthetic physiology response of L. perenne to Cd²⁺ stress, explaining the biomass change affected by Cd²⁺, L. perenne were treated with Cd²⁺(5 mg/L) for 0, 0.25, 1, 3, 6 days respectively. The photosynthetic pigments contents did not change significantly, whereas the gas exchange parameters and the chlorophyll fluorescence parameters were affected significantly. Within 1 d, the change of Pn, Gs and Ci were consistent, the reduce of net photosynthesis rate was caused by stomatal limitation factors. When the plants were treated 3 and 6 d, Pn significantly decased by 24.4% and 23.4% compared with untreated, the recuce was caused by non-stomatal limitation factors. Tr significantly increased by 74.1% when treated 1 d, this promoted Cd transporting to aboveground. Within 3 d, F_v/F₀ significantly increased by 14.4%, 21.0%, 14.4% compared with untreated, and F_v/F_m significantly increased by 3.1%, 3.2%, 3.1% respectively. ΦPSⅡ, rETR and qP significantly decreasd by 25.3%,25.3%,21.1% when treated 6 d, the PSⅡ light reaction ability reduced. The qN significantly decreasd by 15.6% and 41.5% when treated 0.25 and 1 d, then significantly increasd, the photoprotective capacity was increased. Compared with untreated, Y(NO) significantly increased by 30.8% and 37.8% when treated 0.25 and 1 d, and decreased significantly when 3 and 6 d. Y(NPQ) significantly decreased by 36.9% when treated 1 d, whereas significantly incerased by 17.0% when treated 6 d, the extent of photosynthetic apparatus damage was reduced.