Characterizing thermal parameters of a lithium ion battery is a key step to predict the temperature distribution of battery cell modules. In this work, a novel method is developed based on the quasi-steady state heat transfer analysis to determine the thermal conductivity and the specific heat simultaneously. Both prismatic lithium iron phosphate cells and pouch cells with different electrode materials are used in this experimental test. A constant heat flux is applied to the cell surface whereas the heat loss is estimated based upon the temperature drop curve. As such, the quasi-steady state heat transfer can be attained to determine cell thermal parameters. It is observed that cell thermal parameters increase linearly with the increase of the operating temperature. Furthermore, the operating temperature has a more significant influence on the cell specific heat than the thermal conductivity, while the effect of the state of charge has a minimal effect on these two parameters. The current method demonstrates an effective and practical way to determine the thermal conductivity and specific heat of the cell simultaneously. (C) 2019 Elsevier Ltd. All rights reserved.