Under the background of electric energy substitution, to improve the economy in on-grid operation and improve the energy reliability in off-grid of heat pump heating industrial and commercial park, an optimal operation model of industrial and commercial park considering important loads demand during un-planned off-grid is established. On the load side, considering the demand response characteristic of flexible load, the price response characteristic of flexible electric load and the elastic regulation characteristic of flexible thermal load are utilized to regulate the load demand. On the energy storage side, the state of energy level is divided, according to the important electric and thermal loads demand, the reserve capacities during unplanned off-grid at each moment is proposed and calculated, then it is taken as the constraint of energy storage device. The model takes the minimum operation cost as the objective function, the simulation shows that considering the demand of important loads during unplanned off-grid will increase the operation cost slightly, different energy storage capacities and state of energy levels have different operation economics and reliabilities. The model can improve the economy in on-grid operation and ensure the short-term demand of important electric and thermal loads during off-grid can be met, improve the reliability of energy use.