Due to the wide liquid range, good solubility, nonvolatility and designability, ionic liquids (ILs) have been considered as solvent in decontamination field and exhibited enormous potential. In this work, a series of 1‐alkyl‐3‐methylimidazolium molybdate ([CnMIm]2MoO4, n=4, 8, 12, 16) ILs are synthesized and characterized, which could improve the decontamination efficacy of mustard gas simulant 2‐chloroethylethylsulfide (CEES) in H2O2 through solubilization and catalysis. The practicability of functional ILs surfactant aqueous solution in decontamination field are analyzed by considering the influence factors about the critical micelle concentration (CMC), oxidant/CEES mole ratio, types and concentration of ILs, reaction kinetics and reaction activation energy. The results indicate that the decontamination efficacy of CEES is affected by both the concentration of MoO42− and the CMC of ILs. The decontamination efficacy against CEES in the [CnMIm]2MoO4/H2O2 system is accelerated by lengthening ILs cationic alkyl chain.