Ionic liquids (ILs) have biomaterial applications and are used for protein crystallization. The effect of two imidazolium-based ILs, 1-butyl-3-methylimidazolium chloride ([$C_4mim$]Cl) and 1,3-dimethylimidazolium iodide ([dmim]I), on the nucleation kinetics of lysozyme was investigated by determining the nucleation induction time, and nucleation parameters were evaluated. The values of interfacial tension calculated for solutions with added 30 g/L ILs [$C_4mim$]Cl and [dmim]I, and without added ILs were 99.03, 109.7, and 107.3 mJ/$m^2$, respectively. Compared with solutions without IL addition, the critical free energy change, size, and molecular number of critical nuclei decreased and the nucleation rate increased after the addition of [$C_4mim$]Cl. In contrast, the critical free energy change, size, and molecular number of critical nuclei increased and the nucleation rate decreased after the addition of [dmim]I. These new findings provide insights into controlling lysozyme crystallization separation, and present ILs as potentially useful additives for controlling the crystallization of macromolecules.