In order to decrease the energy consumption in municipal sewage treatment process, a collaborative optimization method of biological and ecological combined process was proposed. Collaborative optimization included two main aspects. On the one hand, to reduce the treatment load and energy consumption, the effluent concentration of biological unit was controlled as the permitted influent concentration of ecological unit by distributing the pollutant load dynamically between biological and ecological treatment units in different seasons. On the other hand, in the biological unit, an optimal equation was established with DO concentration, up-to-standard discharge and minimum energy consumption of aeration as the control variable, constraint condition and objective function, respectively. The equation adopted optimization method, and oxygen switch function was introduced to reflect the influence of DO concentration on the maximum specific rate of pollutant degradation quantitatively. Furthermore, by solving the optimal equation in a sewage treatment plant, the pollutants could be removed after 2.3 hours' aeration in the condition of keeping DO value at 4.58 mg/L, and the energy consumption was 31.7 kWh. It shortened the aeration time of 1.7 h and saved energy of 28.3 kWh compared with operating biological unit only, which suggests remarkable energy-saving effect. Finally, the effectiveness of the optimization method was verified by one month's data of a sewage treatment plant.