In developing conceptual watershed concentration models,it is a key to select a proper type of conceptual elements and make arrangement of them.Therefore,the comparison among conceptual elements has a very important significance.Choosing a diffusion-analogy reach as the comparing standard,this paper made a comparative study on conceptual elements in unit hydrograph. The results indicated that comparing with a diffusion-analogy reach,a Kalinin-Milyukov reach,a linear dynamic wave reach and an inverse Gaussion-distribution reach were comparatively similar and frequently applied in actual basins or rivers,but a Muskingum reach and a lag-routing reach are relatively different and have a better application effect in some basins with an obvious lag characteristic or multi-Muskingum reaches in series.