Wind power is one of the most competitive low-carbon energy resources， and is an important element in promoting low-carbon economy. With the output characteristics of wind power generators and its low-carbon emission in mind， the coordination between wind power generators and conventional thermal power generators is analyzed. CO2price signal is introduced and the integrated optimization model is constructed for wind-thermal power systems. Five day-ahead dispatch modes are proposed， which are different from each other in terms of the principle of wind power utilization， day-ahead schedule objective， and ways of wind power participation into day-ahead scheduling. They are compared in a typical wind-thermal power system， with designated system performance indices. Impact of different CO2prices and wind power penetration levels are also analyzed. Simulation results show that wind power priority dispatch with a certain amount of curtailment improves the system performance significantly compared with dispatch that discourages wind power curtailment; Day-ahead dispatch that optimizes both system economy and environmental benefits is better than the conventional mode that is aimed at system economy only; At proper CO2prices， equal participation of wind power with conventional generators is the best way of optimization in achieving both system economy and environmental benefits.