Abstract: An LC-MS/MS method was developed to investigate the pharmacokinetic parameters in healthy Chinese volunteers following single and multiple oral administration of dimemorfan phosphate. A randomized, two-period and crossover study of 12 healthy volunteers was conducted with single-dose of 10 mg or 40 mg of dimemorfan phosphate. Another 12 volunteers were administered with 20 mg. The values of AUC_{0-48 h}, t_1/2, and c_max were(11. 81±14. 46), (52. 60±96. 01 )and(34. 70±29. 59)ng ·h/mL, (12. 11±2. 54), (12. 16±2. 01)and(12. 77±1. 27)h, and(0. 965 3±0. 817 8), (3. 150±3. 451)and(2. 167±1. 650)ng/mL for 10 mg, 40 mg and 20 mg oral administration. The same 12 healthy volunteers as the group of single-dose of 20 mg participated in multiple-dose study, who were administered with dimemorfan phosphate 20 mg, three-time a day until the day-8, AUC_{0-48 h}, t_1/2, and c_max were(115. 9±135. 2)ng ·h/mL, (11. 22±1. 61)h, and(7. 418±7. 010)ng/mL. The accumulation parameters R_cmax and R_AUC were(3. 14±1. 34)and(3. 38±1. 22), respectively. Dose proportional of c_max and AUC was not concluded ranging from 10 mg to 40 mg after confidence interval criteria method. Accumulation occurred after multiple-dose administration. And the results demonstrated significant individual difference.