The voltammetric behaviors of room temperature ionic liquids (RTILs) are affected by many factors, including the structure of cation and anion, experimental conditions, impurities and so on. In this work, the determination of 1-methylimidazole (1-MIm) was explored in three imidazolium ionic liquids by virtue of cyclic voltammetry. On the anodic scans, the oxidation peaks of 1-MIm were observed for tested samples, and the linear correlation of the oxidation peak current against the concentration of 1-MIm could be established by standard addition method. The obtained results showed that the limits of detection reached 20–35 ppm while the limits of quantification were less than 100 ppm. Moreover, the influences of halide ions on the determination of 1-MIm in RTILs were also studied emphatically. It was found that the effect might arise from the reaction between 1-MIm and chlorine or bromine generated from the oxidation of Cl⁻ or Br⁻, since the response of tri-halide was disappeared in the presence of 1-MIm according to the results of cyclic voltammetry and UV–Vis spectroscopy.