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Drainage networks, and the associated channel links and drainage basins, are fundamentalconcepts in earth science. Automatic extraction of drainage networks is an importantcomponent in digital terrain analysis and hydrology analysis such as distributed hydrologicalmodel, soil erosion, etc. Extensive researches have been conducted on extraction of drainagenetworks, but the problem of parallel drainage networks still exist in some flat areas by usingexisting methods. Because calculating flow direction by the cell slope is the vital point ofextracting drainage networks, proposing an effective method to get the right flow direction isnecessary to solve the problem of parallel flow lines. Hence, in this research, wepropose a new drainage networks extraction method combining Priority-Floodand D8 algorithms without filling depressions to resolve the problem of parallelflow lines. The most important advantage of Priority-Flood algorithm is ensuringthe correctness of the flow direction on macro terrain and avoiding the process ofdepression-filling to eliminate the parallel drainage networks is another significant reason.Meanwhile, advanced D8 algorithm takes suitable calculation methods of flowdirection based on different terrains to improve the accuracy of drainage networks,which ensure the water pour out from depression. We compare the results fromthe new method and the J&D algorithm of four different areas including the Alps,the Loess Plateau, the Rocky Mountains and the Qinghai-Tibet Plateau and wecan see that the new method has the obvious advantages of avoiding the parallelflow lines. To evaluate the accuracy of this new method and the J&D algorithm,we use drainage-networks-matching-difference to make quantitative descriptionof errors in the extraction of drainage networks, which is the ratio of the sum ofarea of sliver polygons to the total length of the real drainage networks. Accordingto the results of drainage-networks-matching-difference, it is shown that averagedrainage-networks-matching-difference of new method is better than it of the J&D algorithm,which means the drainage networks extracted by new method are closer to the real drainagenetworks. The algorithm proposed here could reduce parallel flow lines and improve theaccuracy from DEMs. [ABSTRACT FROM AUTHOR]