Abstract: Abstract:【Objective】Roughness coefficient is one of the basic technical parameters in the design and management of surface irrigation system. The spatial variability and poor estimates of roughness coefficient can affect the evaluation and management of surface irrigation system. In this paper, the variability of roughness coefficient and its effect on border irrigation performance were studied. 【Method】The water advance and water depth along the 110m border strips were observed, then the roughness coefficient was calculated by numerical solution of Manning formula, the variability of roughness coefficient and its effect on border irrigation performance were analyzed. 【Result】The results indicate that the average roughness coefficient of bare land is 0.038, its variation degree is moderate. The simulation results for 26 border strips indicate that the biggest relative error of application efficiency and distribution uniformity are 6.48% and 66.67% separately, in which the average and actual roughness coefficient are adopted. 【Conclusion】Therefore the variability of roughness coefficient is not ignored in the actual design and management of surface irrigation.