In order to explore the response and adaptation mechanisms of buckwheat photosynthesis to different improvement measures in salinealkali soil, a pot experiment was set up to determine the photosynthetic light response characteristics of buckwheat under salinealkali soil treated with desulfurized gypsum and magnetized water. With the aim to determine the optimal model which can calculate the photosynthetic characteristic parameters of buckwheat, the light response curves of buckwheat leaf were analyzed by the rectangular hyperbola model, nonrectangular hyperbola model and modified rectangular hyperbola model and exponential model. The results showed that the effect of irrigation with magnetized water on the photosynthetic characteristics of buckwheat was obvious, and the net photosynthetic rate was increased and then decreased with the increase of desulphurized gypsum application, under salinealkali stress. The nonrectangular hyperbola model had the highest simulation accuracy and it can be used as the optimal model to describe the light response curve of buckwheat. Using the optimal light response curve model analysis showed that the photosynthetic characteristic parameters (e.g. dark respiration rate, apparent quantum efficiency, maximum photosynthetic rate, light compensation point, and light saturation point) of buckwheat were significantly higher than that of the other quantity processing in the application of 11t/hm2 desulfurized gypsum. And buckwheat leaves enhanced the adaptive ability of light intensity and promoted accumulation of organic matter. In addition, irrigation with magnetized water could enhance photosynthetic light response of buckwheat. The research result provided a reference for the development of effective regulation methods to alleviate the effects of soil salinealkali stress on crop growth.