The integration of renewable energy sources and the need for more flexible energy systems make TES a crucial technology for industrial applications. This paper starts with flexibility evaluation of metrics and discusses the impact of energy storage on enhancing the flexibility of industrial parks with different source capacity and load characteristics. Precisely, this paper first conducts capacity configuration for each park with the goal of optimizing economy. After obtaining the configuration results, the system is optimized based on flexibility objectives to compare the flexibility improvement effects of energy storage systems in parks with different capacities and load characteristics. The results show that TES can significantly enhance the flexibility potential of the industrial heating system, ensuring the system has sufficient capability to cope with various uncertainties and the full utilization of flexibility can lead to up to 62% savings in operating costs for the system.