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In order to explore the influence of biochar addition on soil hydraulic characteristics under indirect subsurface drip irrigation with biogas slurry, four levels of biochar mass percentages (biochar and soil mass ratios of 0, 1%, 2%, and 5%) and four levels of biogas slurry content (the volume ratio of biogas slurry and water was 0, 1∶8, 1∶6 and 1∶4) were set in the experiment. The biochar and the biogas slurry used wheat straw and cow dung as raw materials, respectively. The soil water holding capacity, soil saturated water conductivity and soil wetting characteristics were investigated. The results showed that soil water holding capacity was increased with the increase of biochar and biogas slurry contents. The Van-Genuchten model can accurately fit the soil moisture characteristic curve of each treatment. Both biochar addition and biogas slurry irrigation alone can increase soil porosity and capillary porosity, and their coupling effects on soil porosity and capillary porosity were more obvious. The soil saturated water conductivity was decreased firstly and then increased with the increase of biochar content, and reached the minimum value when the biochar content was 2%; while it was decreased with the increase of biogas slurry content; moreover, there were an interactive effect between the influence of biochar addition and biogas slurry irrigation on soil saturated water conductivity. The power function can accurately describe the relationship between the wetting front transportation distance and irrigation time under different treatments. The difference of biogas slurry and biochar content among different treatments had obvious effects on the shape of soil wetting body under indirect subsurface drip irrigation, when the biochar content was 1% or 2%, the migration distance of wetting front and volume of wetting body was decreased with the biogas slurry application, the range in the wetting body with high water content (greater than soil field water capacity, 0.3062cm3/cm3) was increased; for treatment with 5% biochar content, the horizontal and vertically upward migration distance of wetting front was decreased with the application of biogas slurry, while the vertically downward migration distance was increased, resulting in an relative smaller area of wetting body with high water content although the volume of wetting body which was as big as that of treatment with 2% biochar content. Taking all indexes into comprehensively consideration, the coupling treatment of Z1∶4B2, and the fine loam soil under indirect subsurface drip irrigation can obtain better soil hydraulic characteristics.