Development of chemical heat pumps and dry sorption systems using solid-gas thermochemical reactors requires determining their optimal operating conditions. Many previous studies particularly noted that the performance of solid-gas thermochemical reaction would be reduced due to low heat transfer rate in the reaction beds. In this study, enhancement of effective thermal conductivity of reaction beds was therefore studied using magnesium oxide/water reaction, which was expected to be utilized for chemical thermal storage in a cogeneration system. High thermal conductive carbon fiber was installed into a reaction bed as a brush in order to be dispersed in the whole reaction bed and improve the effective thermal conductivity. In addition to the experiment, a two-dimensional mathematical model describing heat and mass transfer as well as chemical reaction rate was formulated and solved for its evaluation. Numerical results indicated that increasing the effective thermal conductivity essentially promoted the magnesium oxide/water chemical reaction rate. Qualitative agreement between experimental and theoretical results was obtained. Moreover, optimum operating conditions for a solid-gas thermochemical reactor were also discussed according to the results obtained in this study.