Coastal wetland ecosystem has high primary productivity and is one of the main carbon pools of the earth's ecosystems. However, climate warming and the exotic plant invasion will change the photosynthetic characteristics of plants, resulting in many uncertainties in the stability of carbon pool in coastal wetlands. In this study, we examined the potential effects of climate warming on photosynthetic characteristics of a native (Phragmites australis) and an exotic (Spartina alterniflora) species in Yancheng coastal wetland, Jiangsu Province. The in-sute simulated warming experiments were conducted using passive warming manipulation methodologies. Six open-top chambers (OTCs) and six control chambers were built in the early 2018 in P. australis and S. alterniflora wetlands, respectively. Photosynthetic indices of two species were determined using a portable photosynthetic fluorescence measurement system. The diurnal variation of photosynthesis indicated that, the simulated warming significantly decreased the leaf net photosynthetic rate (P_n), stomatal conductance (G_s), transpiration rate (T_r) and water use efficiency (WUE) of P. alternate, while simulated warming increased these parameters of S. alterniflora in a certain extent. The physiological function of S. alterniflora was enhanced by simulated warming, resulting in the promoted level of photosynthesis. According to the trends of P_n and intercellular CO₂ concentration (C_i), it concluded that the photosynthetic rates of both S. alterniflora and P. australis were driven by non-stomatal limiting factors such as biochemistry or soil nutrients. The modified rectangular hyperbolic model was used to fit the light response curves of two species. The light response curve of P. australis under warming condition jumped down comparing to the controlling condition, while the curve of S. alterniflora under warming condition moved up comparing to the controlling condition. Warming improved the ability of these two species to utilize weak light by reducing the light compensation point (LCP). The simulated warming increased the range of difference between LCP and light saturation point (LSP) of S. alterniflora, thus effectively improving its ability to use photosynthetically active radiation. Warming reduced the dark respiration rate (R_d) of P. australis. Under the stress of elevated temperature, metabolism of P. australis slowed down and the rates of photosynthesis reduced, while S. alterniflora showed the opposite characteristics. Our results suggest that, under warming conditions, the exotic S. alterniflora has a better ability to assimilate atmospheric CO₂ (i.e. carbon sink capacity) than the native P. australis, which is also one of the main reasons that why S. alterniflora has become an invasive species.