An experiment was conducted to ascertain the effects of Cd stress on the PS II chlorophyll fluorescence parameters in leaves of Thalia dealbata and rice in both the intercropping and mono-cropping systems as well as the uptake and accumulation characteristics of Cd by both species. The chlorophyll fluorescence parameters in the leaves under different treatments were measured with PAM-2100 Chlorophyll fluorometer. The contents of Cd in the samples from different treatments were determined using Graphite Furnace Atomic Absorption Spectrometry after wet ashing with HNO₃ -HClO₄. Results showed that the Fv/Fm, YII, qP and rETR of rice decreased with the elevated Cd content in the soil while the qN, NPQ and YNPQ showed the opposite trend, indicating that the Ps II photosynthetic activity was inhibited under Cd stress while the proportion of heat dissipation increased to alleviate the photoinhibition of PS II under the condition of excessive light interception. The YNO of the rice increased in a high level of Cd content, which indicated that the higher level of Cd stress induced damage to PS II reaction centers. The quantum yield of non-regulated energy dissipation increased to a higher level under conditions of excessive light energy. The decrease of Fv/Fm, YII, qP and rETR in T. dealbata were much lower than those in rice with the same level of Cd stress. With a higher level of Cd stress, the YNPQ in T. dealbata increased significantly while the variation of YNO in T. dealbata was not obvious, suggesting that the regulatory energy dissipation mechanism played a major role in the protection of photosynthetic apparatus in Cd stress. With the same soil Cd content, the sequence of Cd content was root > stem > leaf in the rice and stem > root > leaf in T. dealbata. The Cd contents in the root, stem and leaf of rice in the intercropping system were, respectively, lower than those in the monoculture system. The Cd uptake by T. dealbata was significantly higher than that of rice with the same level of Cd treatment. All these results suggested that the PS II reaction center of T. dealbata had a higher tolerance to the Cd stress, and the Cd content of rice in intercropping system could be reduced.