The calcium oxide looping cycle is considered to be one of the promising technologies for CO2 capture from fossil fuel power plants. How to improve CO2 capture and sintering-resistance performance of sorbents during the cycling is a challenge for researchers. An attempt was made to modify CaO sorbents by coal fly ash to improve the CO2 capture capacity and sintering resistance of sorbents, as well as utilize the solid waste. CO2 capture performance of the modified sorbents was investigated and compared with that of pure CaO. The structural properties of the resulting sorbents were characterized by X-ray diffraction (XRD) techniques and N-2 physisorption, showing that the sorbents modified by fly ash presented the formation of Ca12Al14O33 and CaSiO3, as well as a wonderful microstructure. These features enable enhanced sintering resistance and great reactivity enhancement of sorbents, which gave rise to enhanced carbonation conversion and carbonation rate, especially for sorbents modified with the slag/calcined calcium carbonate mass ratio of 1:2 (M2-CaO), of 0.19 g CO2/g sorbents after 30 cycles under severe calcination conditions (3.8 times greater than that of pure CaO). It demonstrates a potential route to enhance CO2 capture performance of sorbents with modification of waste materials such as coal fly ash.