Abstract: The purpose of this research is to provide a basis for the efficient utilization of water resources and the promotion of agricultural water suitable development in Liaoning province. Based on the daily meteorological data of Liaoning province from 1957 to 2017 and crop coefficients in the study area, the water demand rules of major grain crops (spring maize, soybean and rice) and the degree of water demand satisfied by precipitation were calculated and analyzed based on the SIMETAW model. The results showed that: (1) the annual mean water requirements of spring maize, soybean and rice in the whole growing season in Liaoning were 511.8mm, 509.4mm and 605.1mm, respectively, showing an insignificant decreasing trend. (2) The coupling degree of water demand and precipitation in the whole growing season of spring maize and soybean were 0.821 and 0.814, respectively, that is to say, precipitation satisfied 82.1% and 81.4% water demand respectively, and the remaining 17.9% and 18.6% still needed irrigation or supplementary irrigation before sowing. Especially in the western region, the guaranteed rate of coupling degree was only 28.2% and 21.1% when the coupling degree was greater than 0.8. The coupling degree of rice in the whole growing season was 0.464, the guaranteed rate of coupling degree greater than 0.4 was only 69.1% in the whole province, and the guaranteed rate was as low as 36.8% in the western region. (3) In the four subregions of Liaoning, the coupling degree of the three crops was the largest in the eastern region, followed by the central, southern and western regions. The coupling degree of the three crops in each growth stage was the highest in the middle growth stage, followed by the rapid growth stage, and the lowest in the early and mature stages. In recent years, the coupling degree of spring maize and soybean at the early growth stage increased significantly, while the coupling degree of the three crops at the mature stage showed a significant downward trend. The occurrence of spring drought and autumn drought should be paid attention to and irrigation should be supplemented in time for the main grain crops in Liaoning province. Under the current precipitation conditions, it was the most suitable for planting spring maize in Liaoning province, especially in the western region where water resources were scarce, and soybean was most suitable for planting in the eastern and central areas of Liaoning province, while rice was most suitable for planting in the eastern and southern areas of Liaoning province.

Key words: Liaoning province, Grain crops, SIMETAW model, Crop water requirement, Coupling degree between water requirement and precipitation