Thermochemical energy storage, a promising candidate for seasonal solar thermal energy storage, offers an economic solution to mitigate the use of fossil fuels and CO2 emissions due to its large storage density and almost zero-loss long-term storage. The present article explored the potential of the thermochemical seasonal energy storage system using MgO/Mg(OH)(2) system for solar district heating applications in China. The solar district heating model with thermochemical seasonal energy storage system, including the parabolic trough solar collector and a chemical reactor, has been built. The dynamic charging/discharging performance of the seasonal solar thermal energy storage system has been simulated and analyzed by using the real weather data and the practical domestic heating demand. The optimal parameters of the equipment have been identified. And the comparison of the performances between thermochemical seasonal energy storage system and the conventionally used water storage tank system has been carried out for various areas of China. The results indicate that the stored thermochemical energy is able to contribute 94.6% of heating demand in the discharging stage, demonstrating the application potential of MgO/Mg(OH)(2) thermochemical energy storage system in China. The needed solar collector areas of the seasonal thermochemical energy storage system decrease by up to 2/3 compared with those of a water storage tank system in the condition of the similar storage system volume. The advantage of seasonal thermochemical energy storage is more obvious for the case of region with abundant solar energy supply.