Thermal conductivity is an important thermophysical property of ionic liquids (ILs). In this paper, a database for the thermal conductivity of ILs was established by collecting experimental data from literature covering the period from 2007 to 2013, including 359 data points, 45 ILs. The influences of temperature and the alkyl chain length of the cation on thermal conductivity were also discussed. A topological index method was proposed to estimate the thermal conductivity of ILs based on collected data which were divided into training (299 data points, 38 ILs) and testing (60 data points, 7 ILs) sets. The total average absolute deviation between the calculated and literature data was found to be 2.3%, with 2.1% for the training set and 2.9% for the testing set. The topological index method guarantees satisfactory precision with a simple form and can be easily expanded to new kinds of ILs.