Ionic liquids (ILs) are a new class of substances exclusively composed of cations and anions, and they have shown unique physico-chemical properties differing from aqueous ionic solutions and high temperature molten salts. Although many attentions have been paid on ILs, the knowledge of ILs is still limited to experimental try-and-errors and experiences, and it is far away from our need for understanding the nature of ILs, especially for the industrial applications. Therefore, it is indispensably important to study the structure-property relationships and the scale-up principles in the ILs systems, which is the scientific frontier in chemistry and chemical engineering. ILs database have been established, including 2078 kinds of ILs, 41 kinds of physical properties and 54,803 pieces of data. A "Roadmap" was built to screen suitable ILs from numerous combinations of 276 kinds of cations and 55 kinds of anions. A QSPR (quantitative structure property relationship) model was developed for predicting the properties of ILs. Hydrogen bond network structure and its three-dimensional expansibility in ILs were revealed. Molecular force fields for series of ILs were developed, in terms of which molecular dynamic simulation was performed to investigate extensively the micro-structures, interactions and properties.  Besides, a set of novel equipment for in-situ measurement of the transport-reaction coupling performance in ILs was established based on the electric conductive and dynamic characteristics of ILs.  Based on the fundamental research on ILs, an innovative cleaner process of methyl methacrylate, the monomer of perspex, was developed to replace the traditional highly toxic hydrocyanic acid process.  In terms of "ionic switch" principle, a novel de-acidification process of lubricant base oil has been developed, which overcomes many disadvantages such as high energy consumption, heavy pollution in the traditional caustic washing process. Another example is using ILs as catalyst for producing ethylene glycol instead of the traditional direct hydration of ethylene oxide, the new process could save large quantity of energy and significantly reduce wastewater discharge amount.  Acknowledgment This work was supported by the National Science Fund of China for Distinguished Young Scholar (20625618), National Basic Research Program of China (973 Program, 2009CB219900), Knowledge Innovation Program of the Chinese Academy of Sciences (KGCX2-YW-321), National Key Technology R& D Program(2008BAF33B04)and National Natural Scientific Fund of China (50974113, 20903098). References  Zhang S, Lu X, Zhou Q, et al. "Ionic Liquids: Physicochemical Properties", Elsevier, 2009.  Dong K, Zhang S, Wang D, et al. J. Phys. Chem. A, 2006, 110(31): 9775.  Liu X, Zhang S, Zhou, G, et al. J. Phys. Chem. B, 2006, 110(24): 12062.  Dong H, Wang X, Liu L, et al. Chem. Eng. Sci., 2010, 65: 3240.  Y. Diao, R. Yan, S. Zhang, et al. J. Mol. Catal. A: Chem., 2009, 303: 35.  J. Sun, W. Cheng, W. Fan, et al. Catal. Today, 2009, 148: 361.