In order to investigate the response of photosynthetic characteristics of spring wheat under water deficit and plastic mulching conditions in Northwest China, field experiment was conducted with four treatments, including full irrigation without mulching (W1M0), full irrigation with mulching (W1M1), deficit irrigation without mulching (W2M0) and deficit irrigation with mulching (W2M1). The light response curves were monitored with five different light response curve models which were compared. The influences of field mulching and water deficit on photosynthesis of spring wheat were discussed and the applicability of the light response models were evaluated. The results showed that water deficit can reduce the main characteristic parameters, including maximum net photosynthesis rate (Pmax), apparent quantum efficiency (AQY), dark respiration rate (Rd), while light compensation point (LCP) was increased. However, treatments of mulching can slow down the decrease of spring wheat photosynthetic rate effectively. There were obvious differences for treatment W2M0 in the simulation results of the five models, where only Ye Zi-Piao model could well fit the actual values, and especially for the high photosynthetic active radiation section, with the coefficient of determination (R2) greater than 0.9, while the fitting effects of the rectangular hyperbolae model, the non-rectangular hyperbolae model, the exponential model and the kinetics model were poor, which were only about 0.7. Their determination coefficients were in the descending order as Ye Zi-Piao model, non-rectangular hyperbolae model, exponential model, rectangular hyperbolae model and kinetics model.