AIM: To study the pharmacokinetics of phenolic acids from Mailuoning injection in rats. METHODS: SD rats were given a single i.v. administration dose of Mailuoning injection 10 mL/kg, plasma and urine were collected before and after injection. Phenolic acid components in plasma and urine were measured by LC/MS. Pharmacokinetic parameters were determined from the plasma concentration-time data and urinary excretion-time data with the DAS software package. RESULTS: After i.v. of Mailuoning injection, chlorogenic acid (CGA), 1, 5-dicaffeylquinic acid (1,5-DCQA), 3, 4-dicaffeylquinic acid (3,4-DCQA), 3, 5-dicaffeylquinic acid (3,5-DCQA) and caffeic acid (CA) were quickly excrectioned. The t1/2 of CGA, 1,5-DCQA, 3,4-DCQA, 3,5-DCQA and CA were 0.649, 0.334, 0.479, 0.486 and 0.330 h, respectively. AUC0-∞ were (22.522±2.716), (0.353±0.062), (3.620±1.246), (5.287±1.627) and (2.257±0.360) mg·L-1·h, respectively. After i.v. of Mailuoning injection, CGA, 1,5-DCQA, 3,4-DCQA, 3,5-DCQA and CA can all be detected in the urine. The amounts of CGA, 1,5-DCQA, 3,4-DCQA, 3,5-DCQA and CA excreted from urine during 0-24 h were (122.22±26.49)%, (3.30±1.26)%, (0.24±0.11)%, (1.93±0.77)% and (18.61±4.99)% of dose given in rats, respectively. CONCLUSION: After i.v. of Mailuoning injection, phenolic acids can be excreted quickly. Only a small quantity of 1,5-DCQA, 3,4-DCQA, 3,5-DCQA and CA were excreted from urine. 3,4-DCQA and 3,5-DCQA may be metabolized into CGA in the rat plasma.