Abstract: To study the effects of waterlogging stress on photosynthetic parameters of waterlogging-tolerant (WT) and susceptible rapeseed lines, 9 WT lines and 7 susceptible lines were selected and fully submerged on five leaves stage. Photosynthetic parameters were detected before waterlogging and 4 days (D), 8 D, 12 D and 16 D after waterlogging. According to the results, the photosynthetic rate (Pn) of the rapeseed lines increased after 4 days of waterlogging, but declined hereafter. The drop rate of WT lines (16.0%) was smaller than the susceptible lines (32.4%) after 16 days of waterlogging. The transpiration rate (Tr) of the WT lines kept on rising after the waterlogging treatment, but the susceptible lines raised to the peak (4.35±0.87) after 12 days of waterlogging and then declined. The stomatal conductance (GS) of the WT lines increased along with days of treatment, but the susceptible lines raised to the peak (0.61±0.11) after 12 days of waterlogging and then declined. The intercellular CO2 concentration (Ci) of the rapeseed lines increased to the peak after 12 days of waterlogging and then declined. The water use efficiency (WUE) of the rapeseed lines declined significantly after waterlogging, but the WUE of the WT lines declined slower than the susceptible lines. The results showed that the photosynthetic adjusting capacity of WT lines could decrease the drop rate of Pn and delay the damage of waterlogging on the plants at a longer time than susceptible lines.