Thermodynamic analysis for an integrated solar thermochemical energy storage system was conducted to examine its energy and chemical conversion performances. Detailed mathematical description for the transportation process of radiation energy was given to obtain the input solar power to the solar receiver/reactor. Plug-flow model was used to determine the species concentrations and temperature distributions of the solar reactor combined with kinetic models. Then concentrations of species and temperature at outlet of solar reactor were used in the overall thermodynamic model to investigate the effects of key parameters on thermal performance of the system. The results shown that each of the key parameters (initial molar flow rate, diameter and length of reactor, initial molar ratio of CH4/CO2, and absorption coefficient) produced both of positive and negative influences on energy and chemical conversion performances. In order to fully utilize the input energy and feed gas, mass transfer/heat transfer and chemical reaction rate should match with each other. So in both single factor analysis and transient operation condition analysis, the operation parameters were optimized which significantly improved the cycle work efficiency eta(cycle) (from 17.72% to 34.04% on 12:00 of Summer Solstice, and from 19.53% to 33.37% on 12:00 of Winter Solstice). (C) 2018 Elsevier Ltd. All rights reserved.