[Objective] The process of slope runoff and sediment yield and its influencing factors of different types of biological soil crust were clarified in order to provide theoretical basis for evaluating soil and water conservation function of biological soil crust.[Methods] The common cyanobacterial crust and moss crust in the Loess Plateau region were selected as the research objects, to systematically study the effects of crust types and destruction on runoff and sediment yield under the condition of rainfall.[Results] ① The coverage of biocrusts could significantly enhance the cohesion of soil surface. Soil surface cohesion of cyanobacterial crust and moss crust were 1.52 and 1.25 times higher than that on bare land (4.53 kPa), respectively. After the biocrusts were destroyed, the soil cohesion of soil surface was still higher than that of bare land, which was 1.22 and 1.10 times of that of bare land, respectively. ② Biocrusts could increase slope runoff and inhibited slope sediment yield. Compared with bare soil condition, cyanobacterial crust and moss crust increased the total runoff by 21.64% and 55.75% respectively, and decreased the sediment yield by 94.06% and 89.24% respectively. After the biorusts were destroyed, it could still promote runoff and inhibit sediment yield. The runoff was increased by 58.76% and 59.66%, and the sediment yield was decreased by 16.18% and 29.45%. ③ With the increase of cumulative runoff, the increasing rate of cumulative sediment yield from large to small was as follows:bare land > cyanobacterial crust removal > moss crust removal > moss crust coverage > cyanobacterial crust coverage. Cohesion was an effective indicator of biological crust to inhibit soil erosion. With the increase of cohesion, the sediment yield decreased linearly (R²=0.66).[Conclusion] By increasing the biological soil crust coverage and prevent the biological crust from being damages, its function of soil and water conservation could be maximized.