In order to explore the effect of applying biochar on soil water diffusion and solute dispersion in sloping farmland in black soil area, the biochar effect test was carried out on a typical slope of 15°, 3° and 5° in 2016—2019. The effects of carbon on soil bulk density, porosity, organic matter content, Boltzmann transformation parameter (ξ), unsaturated soil water diffusion rate D(θ), and unsaturated soil hydrodynamic diffusion coefficient Dsh(θ) in the single application of biochar were analyzed. The results showed that the soil bulk density was significantly decreased, and soil porosity and soil organic matter content were significantly increased in the soil within a year after the addition of biochar. And the changing rate of each index was decreased with the increase of slope and the extension of carbonation period. Among the three factors of slope, year and whether to apply biochar, the most significant effects on soil bulk density, porosity, organic matter content were whether or not to apply biochar. Biochar increased the ξ, and the ξ was increased with the slope of soil, and the length of carbon was reduced year by year. From 2016 to 2019, D(θ) and Dsh(θ) were both increased rapidly with the increase of soil water content (θ). When θ≤0.42cm3/cm3, biochar inhibited soil moisture diffusion, and when θ>0.42cm3/cm3, biochar promoted soil water diffusion. When θ≤0.36cm3/cm3, biochar inhibited the dispersion of NaCl solution in the soil, and when θ>0.36cm3/cm3, biochar can promote the dispersion of NaCl solution in the soil. The soil water content in experimental zone was in the range of 0.20~0.35cm3/cm3, thus the biochar had an inhibitory effect on water diffusion and NaCl solution dispersion, and the effect of biochar on water diffusion and solution dispersion was decreased with the increase of slope and prolonged years after charcoal application.