Abstract: Field roughness coefficient is an important hydraulic parameter of influencing field flow movement. Field roughness coefficient for different soil surface conditions were studied The main influence factor of field roughness coefficient in bare land and plowed land was analyzed. The soil surface embossing degree, rhizome relative width and rhizome height are also main effective factors of field roughness coefficient in the crop land. Embossing degree, rhizome relative width and rhizome height in different surface conditions were measured in field, and the tests of field flow movement were done. Combination of the zero inertia model and optimization method which are established the optimization model of field roughness coefficient. Based on the measured value and the optimization model of field roughness coefficient, the calculated values of field roughness coefficient in different cultivated land were obtained. Hereby, regression equations of field roughness coefficient in bare land, plowed land and crop land were established. The equation was checked by field experimental data, the results indicated that the model was reasonable and accurate. The results are reference to design field irrigation system rationally for improving irrigation quality.