[Background] Soil particle size distribution (PSD) is one of the important indicators of soil physical properties, is also a key parameter in erosion and sediment nutrient enrichment research. In recent years, as a relatively new method of measuring particle size distribution(PSD) compared to the classical method of the pipette method, the laser method has been widely applied to the PSD of soil and river sediment, and gradually applied to the PSD of eroded sediment. [Methods] In order to obtain thedifferences and transformation relations between the PSDs determined by the two methods in the Black Soil Region, 18 eroded sediment samples of a small watershed during the snow melting were measured and analyzed by the laser method and pipette method. In the present study, the S3500 manufactured by the US Microtrac company were used for measuring the samples of laser method. [Results] Results showed that the D50 (Median Diameter) and MWD (Mean Weight Diameter) using the laser method were obviously higher than those using the pipette method, which was consistent with the conclusion of the sediment size distribution curve. Although the D50 and MWD measured by two methods varied widely, significant relationships were found between the two methods for the D50 and MWD: yD50 =1.609xD50 -13.743(R² = 0.960, P < 0.001), yMWD = 0.962xMWD - 0.002 (R² = 0.999, P < 0.001). The PSD was analyzed according to the US soil texture classification system. The sand and clay contents using the laser method was under-estimated by 2.6% and 31.5% respectively compared to that using the pipette method, while the silt content of the laser method was over-estimated by 34.1% compared to that of the pipette method. However, significant linear transformation relationships were observed between the laser method and the pipette method for the clay content, silt content and sand content of the eroded sediment: ysand = 0.864xsand + 3.844 (R² = 0.965, P < 0.001), ysilt = 0.725xsilt - 11.858(R² = 0.897, P <0.001 8), yclay = 0.879xclay + 32.772(R² = 0.918, P < 0.001). According to the US soil texture classification, the sand content was further classified into the above medium, fine and very fine, while the silt content into the coarse and fine. The laser method obviously caused the over-estimation of the content of the fine silt by 34.1%, while there were not significant differences between the two methods for the other four contents. There were significant linear transformation relationships between the two methods for the above medium sand: y1 =0.948x1 +0.092 (R² =0.996, P <0.001), fine sand: y2 =0.943x2 - 0.234 (R² = 0.912, P < 0.001), coarse silt: y4 = 0.730x4 + 3.407 (R² = 0.924, P <0.001), and fine silt: y5 =0.517x5 -1.088(R² =0.896, P <0.001), except the very fine sand: y3 =0.699x3 +4.436 (R² =0.764, P <0.001). [Conclusions] The laser method cannot be used for directly measuring the PSD of eroded sediment, as obvious difference existed between two methods. However,significant linear transformation relationships for each grade were observed between two methods, thus the laser method can be effectively used to measure the PSD of eroded sediment, which can save our time when it comes to sedimentation, pipet samplers, drying and so on.