Ionic liquids (ILs) have a wide range of applications due to their many beneficial properties. However, the production cost of ILs is still high, which is limiting further industrialization. Hence, in-depth studies of the reaction kinetics and phase changes are essential to optimize the synthesis processes for ILs and the key equipment involved. An in-situ low-field magnetic resonance imaging (MRI) device was used to monitor the reaction kinetics and phase changes that occurred during the synthesis of ILs in real time. Quantitative analysis of the ILs components in the reaction system was performed using an established two-component analysis model via 1H low-field nuclear magnetic resonance (LF-NMR) relaxometry data. This analysis allowed investigating the effects of haloalkanes chain length, halogen species, stirring speed, and temperature on the reaction kinetics of the synthesis of imidazole-based ILs. Through the detected spatiotemporal T2 distributions of the phases state during the solvent-free synthesis of the 1-buty-3-methylimidazole ([C4mim]Br) IL by reacting 1-bromobutane (BuBr) with 1-methylimidazole (MIM). This study provided a set of fast, convenient, and non-destructive technical means for the detection of different aspects of the synthesis of ILs, including detection of the residual amount of ILs in organic solvents. Meanwhile, further exploration of using low-field MRI to study the combined mass transfer and reaction kinetics in ILs systems as the studied ones could be expected.