The effects of three kinds of background electrolytes (NaCl, Na₂SO₄ and Na₃PO₄) on the adsorption and desorption of humic acid in the dairy manure biochar were studied. Results showed that under the effect of the three kinds of background electrolytes, the dairy manure biochar adsorption capacity and adsorption rate increased with the increase of liquid humic acid concentration, however, the increasing speed gradually slowed down. Compared to the three kinds of background electrolytes, NaCl had the highest adsorption capacity and adsorption rate of humic acid in dairy manure biochar, The range of adsorption capacity was 0.13–6.10 mg/g, the range of adsorption rate was 25.40%–87.14%. With the increase of the concentration of adding liquid humic acid, the desorption capacity of adsorption state humic acid gradually increased, and the desorption rate gradually decreased. Compared to the three kinds of background electrolytes, Na₂SO₄ had the highest desorption rate of adsorptive humic acid in dairy manure biochar, and the range of desorption capacity was 0.15–0.78 mg/g. the concentration of liquid humic acid was 140 mg/L, the desorption capacity of the three kinds of background electrolytes to the adsorptive humic acid of dairy manure biochar have reached the maximum value, the order of desorption capacity was Na₂SO₄ >Na3PO4>NaCl. Na₃PO₄ had the greatest effect in the desorption rate of humic acid, the range of desorption rate was 17.24%–90.55%, NaCl had the minimal effect in the desorption rate of humic acid, the range of desorption rate was 8.22%–53.54%. The isothermal adsorption curves and isothermal desorption curves of the three kinds of background electrolytes in humic acid were fitted with Langmuir, and the correlation coefficients were significant. The results showed that the effects of different background electrolytes to dairy manure biochar on the adsorption and desorption of humic acid were studied, which provided a theoretical reference for soil fertility and soil fertility.