The effectiveness and mechanism of biochar adsorption of sulfadiazine (SDZ) and florfenicol (FFC) in purple soil with different raw materials and pyrolysis temperatures were investigated by batch equilibrium experiments using calcareous purple soil, one of the most widely distributed dry soils in southwest China. The results showed that the Freundlich isothermal adsorption model could better fit the adsorption isotherms of biochar, purple clay, and biochar-amended purple clay for antibiotics, and all of them were spontaneous physical adsorption processes, except for the low-temperature biochar, where the adsorption process was non-spontaneous. The sorption capacity constants (KF) of rape biochar and rice biochar were generally not significantly different (P > 0.05), and those of low-temperature biochar and high-temperature biochar were generally significantly different (P < 0.05), SDZ (KF = 0.02~0.45) and FFC (KF = 0.09~0.40) were both weakly adsorbed in the purple soil. After biochar was applied to purple soil, the adsorption capacity constant (KF) of SDZ (FFC) of biochar improved purple soil was 0.60 ~ 452.00 times (3.15 ~ 278.89 times) higher than that of purple soil, the adsorption capacity constant (KF) of low-temperature biochar improved purple soil was 3.95 ~ 120.00 times (2.19 ~ 9.10 times) higher than that of low-temperature biochar, and the adsorption capacity constant (KF) of high-temperature biochar improved purple soil was -0.61 ~ 26.45 times (- 0.75 ~ 0.40 times) higher than that of high-temperature biochar, the adsorption performance of low-temperature biochar and purple soil for the tested antibiotics had a superimposed effect, while the high-temperature biochar did not exert its original adsorption performance in the biochar-amended purple soil, and the adsorption capacity constants (KF) for sulfadiazine and florfenicol even showed a tendency to decrease, with the maximum decrease up to 61.00% and 75.00%, respectively.