Abstract: The aim was to obtain the basic data for development and registration the sulfamonomethoxine (SMM) suspension preparation.The pharmacokinetics of SMM and SMM-Na suspension injections and SMMNa injection were studied in healthy pigs. 18 pigs of 3 groups were administered muscularly with SMM at 100 mg/kg body weight in single.The SMM concentrations in plasma were analyzed by high performance liquid chromatography (HPLC).The pharmacokinetic parameters were calculated by MCPKP program. The pharmacokinetic processes of 3 preparations were all fitted to twocompartment open model with first-order absorption. The main pharmacokinetic parameters were as follows: t1/2α (2.86±0.85) h，t1/2β (45.57±8.06) h，AUC (712.04±108.20) mg·L-1·h，Cmax (12.16±0.52) μg/mL for the SMM suspension; t1/2α (7.90±1.21) h, t1/2β (24.87±12.92) h, AUC (1 489.78±164.63) mg·L-1·h, Cmax (97.86±10.24) μg/mL for the SMM-Na suspension; t1/2α (0.10±0.04) h， t1/2β(6.20±0.57) h，AUC (1 080.83±93.78) mg·L-1·h，Cmax (84.30±4.26) mg/L for the SMM-Na injection. Though SMM suspension injection was eliminated very slowly, its plasma-drug concentrations were low with a short effective plasma-drug concentration time, and were difficult to meet the clinic treatment requirement. SMM-Na suspension injection showed a long effective plasma drugconcentration time with high plasma-drug concentrations and it was an excellent delayed-release preparation.