The adsorption and desorption of ammonium by biochar affects the nitrogen fixation effect of soil. To explore the effect of tea residue biochar on the adsorption-desorption of NH₄⁺-N in tea garden soil, reduce nitrogen leaching in soil, and improve nitrogen use efficiency, through a simulated culture experiment, the equilibrium adsorption method and HCL desorption method were used to study the adsorption-desorption of NH₄⁺-N characteristics in tea garden soil in which the biochar that prepared at different pyrolysis temperatures was differently added (0.35%, 0.70%, 1.40%, 2.80%). The results showed that the application of biochar could effectively enhance the adsorption of NH₄⁺-N by tea garden soil and the enhancement increase with the increase of biochar addition. Under the same addition, the adsorption amount of NH₄⁺-N in the tea garden soil treated by four kinds of biochar trended as BC400 > BC300 > BC500 > BC600. The CEC content of biomass carbon was the main factor affecting the ability of soil to adsorb NH₄⁺-N. The adsorption process of NH₄⁺-N by soil, which was dominated by monolayer adsorption, reached a significant level by matching the Langmuir equation (0.953 7<R²<0.995 5). After the application of biomass charcoal, the soil produced a known absorption hysteresis, which effectively reduced the desorption rate of NH₄⁺-N in tea garden soil, and the desorption rate of BC400 was the lowest. Tea residue biochar can enhance the adsorption of NH₄⁺-N in soil, reduce the desorption of NH₄⁺-N, improve the ability of soil to absorb nitrogen, and the treatment of BC400 with 2.80% addition showed the best effect.