Sorption and desorption are an important process that will influence the behavior of transport, transform and bioavailability of antibiotics in soils. In this study, batch and column experiments were carried out to study the effects of biochar application on the sorption-desorption process and leaching behaviour of three typical sulfonamide antibiotics (Sulfadiazine, SD; Sulfamethazine, SM2; and Sulfamethoxazole, SMZ) in a sloping cropland purple soil which is distributed widely and abundantly in Sichuan hilly area. Biochar was applied to the tested soil with the amounts of 0 (B0), 39.75 t/hm² (B1) and 198.75 t/hm² (B2) respectively and went through a half-year dry-wet alternate aging process (from May to November). The results showed that the adsorption capacity of three sulfonamides followed the order of SD>SMZ>SM2; Compared with B0, addition of fresh biochar enhanced the adsorption of SD, SM2 and SMZ, among which the improvement for SM2 was significant (P<0.05), but such effect became less obvious after the ageing process. As for the desorption process, the value of Freundlich coefficient K_f of three sulfonamides followed the order of SD>SMZ>SM2, indicating that SD had the highest adsorption capacity and lowest desorption capacity with SM2 inversely. The hysteresis coefficient (H) of three sulfonamides followed the order of SDn. It suggested that SM2 desorbed the fastest from purple soil due to the lowest appetency, while SM2 behaved oppositely. Three sulfonamide antibiotics transported more slowly in B1 compared with B0.