The introduction of various low-carbon factors will impose significant constraints on traditional power dispatch. In a carbon-constrained world， apart from security and economy， which are the most important targets in traditional power dispatch mechanisms， more attention should be paid to the reduction of CO2emission in power system operation. A new mechanism is proposed for lower-carbon power dispatch that takes a comprehensive consideration of security， economy and CO2emission reduction. The background and definition of lower-carbon power dispatch mechanism are analyzed and the characteristics of lower-carbon power sources are defined. The relations between power generation and CO2emission of various power plants are formulated and divided into three categories， the near-zero emission power sources， normal fossil fuel-based power plants， and carbon capture power plants. On this basis， a preliminary model is presented to formulate a lower-carbon power dispatch mechanism that takes into account the low-carbon power techniques， cost and emission constraints. The impact of the introduction of various low-carbon factors on the optimum power generation schedule is analyzed with examples.