In this study, calcareous purple soil, one of the most widely distributed dryland soils in southwest China, was selected, batch equilibrium experiments were used, in which 4 kinds of biochars were prepared, including rape and rice straw biochars at low and high temperatures, and then the effectiveness and mechanism of biochar adsorption of sulfadiazine (SDZ) and florfenicol (FFC) in soils were determined and compared. The results showed that Freundlich isothermal adsorption model could better fit the adsorption isotherms of antibiotics under all treatments. Except for the low-temperature biochar, the other treatments were spontaneous physical adsorption processes. The sorption capacity constants (K_F) for SDZ and FFC were not significantly different between of rape and rice straw biochars, but significantly different between low-temperature and high-temperature biochars (P<0.05). And SDZ (K_F=0.02-0.45) and FFC (K_F=0.09-0.40) were both weakly adsorbed in soil. After biochar was applied to purple soil, K_F for SDZ and FFC of biochars improved purple soils were 0.60-452.00 times and 3.15-278.89 times higher than those of purple soil, K_F for SDZ and FFC of low-temperature biochar improved purple soils were 3.95-120.00 times and 2.19-9.10 times higher than those of low-temperature biochar, and K_F for SDZ and FFC of high-temperature biochar improved purple soils were -0.61-26.45 times and -0.75-0.40 times higher than those of high-temperature biochar. In conclusion, a superimposed effect was found in the adsorption performance of low-temperature biochar and purple soil for the tested antibiotics, which was not observed for high-temperature biochar, even K_F for SDZ and FFC showed a decreasing tendency, with the maximum decrease up to 61.00% and 75.00%, respectively.