In order to improve the energy utilization rate of cogeneration units and meet the urban heating demand, the current situation of cogeneration, a heat supply technology, was expounded. A optimized cogeneration technology was proposed for 300 MW air-cooled units in a power plant. The technology combined the backwater of low-temperature heat supply network, high back pressure of unit and heat pump technology. It deeply recoverd the waste heat of steam turbine condensation and realized the cascade utilization of heat energy. The results of estimation showed that compared with the traditional steam extraction and condensation cogeneration technology, the hourly heating capacity of the optimized technology increased from 446.23 GJ/h to 576.34 GJ/h and the heating efficiency of the heating network increased from 46.65% to 62.14%.