Abstract: The SIMDual Kc model has been widely used to implement the dual crop coefficient (Kc) approach, and then estimate the crop evapotranspiration in the water balance of soil after irrigation. This study aims to evaluate the suitability of the SIMDual Kc model for the summer maize under drip irrigation in southern Xinjiang China. The evaporation, transpiration, and evapotranspiration were also determined using the SIMDualKc model. A field experiment was conducted at the Hongqipo Forestry and Fruit Experiment Base in Hongqi Village, Wensu County, Aksu Region (E80°20′, N41°16′) in 2022 and 2023. Four gradients of irrigation were set under the conditions of plastic film mulching and bare land drip irrigation. The variety of maize was taken as the Xinyu 9. A bottomless measuring pit was also selected from the Aksu Experimental Base. A total of eight irrigations were carried out in the growth period. The amount of irrigation was calculated during the cycle using the FAO-56 Penman-Monteith model. The meteorological data was collected in the experimental area. The stable carbon isotope technique was also utilized to calculate the actual transpiration of summer maize. The water balance was obtained to calculate the crop evapotranspiration. A micro-lysimeter was also utilized to measure the evaporation in the field. The parameters of the improved model were calibrated, such as the crop plant height, leaf area index, crop root depth, and soil texture. The SIMDual Kc model was constructed to estimate the evapotranspiration, soil evaporation, and crop transpiration of summer maize under plastic film mulching and bare land drip irrigation. The results show that the SIMDual Kc model performed better to estimate the evapotranspiration of the summer maize with drip irrigation. The measured values were in better agreement with the simulated ones. The coefficient of determination between the simulated and the measured values was 0.66~0.95, in terms of the evapotranspiration, evaporation, and transpiration of summer maize with drip irrigation in the mulched and unmulched land. The regression coefficient was 0.86~1.14. The consistency index ranged from 0.69 to 0.99, and the root-mean-square error ranged from 0.14 to 19.41 mm, while the normalized root-mean-square error was in the range of 9.63% to 28.32%. An optimal combination of the parameters was achieved in the SIMDual Kc model applicable to summer maize with the mulched drip irrigation in the study area, where there were 10 mm in depth of evaporation layer, 24 mm in total evaporation water, and 9 mm in easy evaporation water. Among them, the crop coefficients were 0.15, 1.2, and 0.5 in the initial, middle, and later stages, respectively. In the unmulched drip irrigation, the crop coefficients were 0.15, 1.15, and 0.45 in the initial, middle, and later stages, respectively. An optimal combination of parameters was 10 mm in depth of the evaporation layer, 22 mm in total evaporation water, and 9 mm in easy evaporation water. Furthermore, the crop evapotranspiration was simulated during the entire growth period. The basic crop coefficient shared the trend of increasing first and then decreasing. Moreover, crop transpiration was positively correlated with the basic crop coefficient. The basic crop coefficient varied greatly in the soil evaporation amount and coefficient. The plastic film mulching also increased the basic crop coefficient. The SIMDual Kc model also shared the high accuracy to simulate the evaporation, transpiration, and evapotranspiration of summer maize under drip irrigation. The resulting parameters of this model can be expected to estimate the evaporation, evapotranspiration, and transpiration of summer maize. A great contribution can be gained for the optimal irrigation regime and evapotranspiration parameters of local summer maize under drip irrigation. The finding can also provide a theoretical basis to quantify the evapotranspiration, evaporation, and transpiration of summer maize during each growth period in southern Xinjiang.