Abstract:Changes in Photosynthetic parameters were examined of Cassia data L. and Syzygium cumini （Linn.） Skeels grown on waste residue of oil shale from Maoming Petrochemical Company as polluted site, and at Maoming forestry institute as control site. Results showed that absolute values of net photosynthetic rate, stomatal conductance, and transpiration rate in C. data, were higher than those in S. cumini at most hours in the daytime at both sites. Reductions in net photosynthetic rate and water use efficiency in C. data. were greater than those in S. cumini, whereas, stomatal conductance was the contrary, which might be related to the water content in soil at different experimental sites. It was shown that S. cumini was more resistant to oil shale pollution than C. data. More comprehensive physiological indexes in selecting pollution-resistant plant species are desirable.