The heat storage characteristics of buildings have great potential in promoting the absorption of renewable energy and improving the flexibility and economical efficiency of the combined heat and power system. In this paper, a building with double-tube hot water heating system in a distributed combined cooling, heating, and power (CCHP) system is studied. Based on the analysis of the performance of radiators and the heat consumption of buildings, the heat storage model of buildings is established, which determines the room temperature in real time from the temperatures of supplied water and outdoor environment. Sensitivity analysis of several variable parameters is conducted to investigate the influence of minor disturbance of a parameter on indoor temperature. On this basis, this paper further establishes an operational optimization model of a distributed CCHP system considering the heat storage characteristics of buildings, taking the minimum daily operating cost as the objective function, and the indoor temperature limits, the supply and return temperature limits as constraints. The simulation results show that the heat storage characteristics of buildings can transfer the load, charge the heat at low electricity price and discharge at high, effectively improving system's economical efficiency and flexibility.