The hybrid genetic algorithm combined with Levenberg-Marquardt optimization algorithm was established to estimate root water uptake model parameters. A series of numerical experiments and root water uptake were conducted to verify the model. The results indicated that the optimized value of the root water uptake model parameter optimized model with the hybrid genetic algorithm has a higher precision. The time and space interval of soil water content had a great influence on the root water uptake model parameter's optimized precision. In practice, it is recommended to choose 5～10d for time interval and 5～10cm for space interval. Furthermore, the inverse method was applied to simulate the average root water uptake rate distributions of cotton. The simulated results showed that the optimized model solving the root water uptake model can simulate the root water uptake of cotton, to solve the root water uptake parameter.