A new approach for the determination of methylephedrine hydrochloride (ME), thebaine, codeine phosphate (CP), and acetylcodeine (AC) was established by CE-ECL with ionic liquid (1-butyl-3-methylimidazolium tetra fluoroborate). The conditions for the CE separation, ECL detection, and the effect of ionic liquid were systematically investigated. Under the optimal conditions, the four analytes were well separated within 8 min using 1-butyl-3-methylimidazolium tetrafluoroborate as additive in the electrophoretic buffer. The concentration detection limits of ME, thebaine, CP, and AC were 2.1 x 10(-8), 1.4 x 10(-7), 6.3 x 10(-8), and 3.6 x 10(-8) mol/L (S/N=3), respectively. The LOQs (S/N = 10) in real human urine samples were 7.6 x 10(-7) mol/L for ME, 3.6 x 10(-6) mol/L for thebaine, 6.5 x 10(-7) mol/L for CP, and 4.6 x 10(-7) mol/L for AC, respectively. The recoveries of four alkaloids at different levels in human urine samples were between 90.0 and 103.5%. The developed method was successfully applied to the determination of four drug alkaloids in human urine samples.