The research on extraction of water systen is more at present and the method is different,but the research on different methods is less.The paper took Fujian as an experimental region and used DEM. elevation data to compare the results of water system extracted by single flow direction algorithm (D8 algorithm) and multiple flow direction algorithm (Dinf algorithm).The results show that the quality of river network extracted by Dinf algorithm is better than that of D8 algorithm, but the calculation process of Dinf algorithm is more complicated than that of D8 algorithm. Among the even and large river area, Dinf algorithm improved the problem of parallel pseudo channel which is easy extracted by D8 algorithm.The river channel extracted by Dinf algorithm is more smooth and natural.