A viscosity model for ionic liquids (ILs) at high pressure based on Eyring's absolute rate theory was presented, in which the flow energy was considered as two parts: the activation energy and the vacancy formation energy. A reference state was introduced to simplify the calculation process. Peng-Robinson equation, Soave-Redlich-Kwong equation and group contribution method were chosen to estimate the compressibility factor required in the present model. The experimental viscosity data of 25 ILs at the temperatures from 273.15 K to 433.15 K and pressures up to 300 MPa were used to test the present model. The overall average absolute relative deviation of the present model coupled with the three compressibility factor calculation methods are 2.03%, 2.01% and 1.92%, respectively. The accuracy effect of the compressibility factor calculation method on the performance of the present model was also investigated. Parameters of the present model were generalized in terms of the carbon numbers of the cation alkyl chain for the homologous series of ILs in order to improve the predictive ability. (C) 2017 Elsevier B.V. All rights reserved.