Abstract: In order to reduce the loss of fulvic acid and to improve its utilization, the effect of dairy manure biochar on fulvic acid adsorption-desorption was investigated by using indoor experiment. The Langmuir and Freundlich equations, pseudo-first-order model, pseudo-second-order model and intra-particle diffusion equation were used to study the effects of dairy manure biochar on the adsorption and desorption of fulvic acid by the three kinds of electrolytes (NaCl, Na₂SO₄ and Na₃PO₄). The results show that the isothermal adsorption process of dairy manure biochar on FA was in accordance with the Langmuir equation, and the kinetic equation was in accordance with the pseudo-second-order equation. It was significantly different for the dairy manure biochar on the isothermal adsorption and desorption processes of FA with the three kinds of electrolytes, the order of adsorption capacity and adsorption rates were NaCl>Na₂SO₄>Na₃PO₄, the order of desorption capacity and desorption rates were Na₃PO₄>Na₂SO₄>NaCl, the adsorption intensity and desorption intensity of MBC also reacted to this rule. It was significantly different with the three kinds of electrolytes on adsorption and desorption kinetics of FA by dairy manure biochar, and the order of adsorption capacity and adsorption rates were NaCl>Na₂SO₄>Na₃PO₄, the order of desorption capacity and desorption rates were Na₃PO₄>Na₂SO₄>NaCl. The results from the Intra-particle diffusion equation also showed the simultaneous control of the external diffusion and the diffusion of inter-particle. In summary, NaCl has the strongest effect on the adsorption of FA by the dairy manure biochar, which is beneficial for the enhancement of soil fertility, the improvement of the organic pollutants adsorption capacity, and the improvement of the ecological environment.