Abstract: The parameters of root-system water-absorbing model and the water and heat transportation model of crop based on experimental data were determined, which were solved by using finite difference and iterative methods. The simulations of water and heat transportation were performed under straw mulch on water and heat of summer corn farmland. The results show that these models can describe the laws of water and heat transportation based on different mulch rates in the summer corn farmland, i.e., the soil water content decreases in the 0～40 cm and increases in the 40～100 cm, the soil temperature decreases in the 0～20 cm. The transportation laws of soil moisture and soil temperature are shown as follows: mulch rate 150%> mulch rate 100%> mulch rate 50%> no mulch under different mulch rates. Straw mulch has the obvious effects of water saving and temperature controlling, which lays a theoretical foundation for crop high-yield under water saving irrigation condition.