The occurrence phases of calcium in raw coal and fly ash from circulating fluidized bed(CFB) were identified by X ray diffractometer(XRD) and scanning electron microscope energy spectrum(SEM EDS). According to the difference of chemical reaction characteristics of different calcium containing phases, the quantitative analysis method of calcium containing phases in CFB fly ash was established by using the step by step extraction method of sucrose and sodium thiosulfate(Na2S2O3) solution. The calcium in the CFB raw coal exists in the form of dolomite, while in the CFB fly ash in the forms of CaO, CaSO4 and calcium feldspar. The content of CaO, CaSO4 and calcium feldspar in CFB fly ash is 503%, 245% and 544% respectively. It is further found that most of CaO and CaSO4 exist on the surface of fly ash. Calcium feldspar adheres to the surface of a mullite and iron rich phase, and symbiosis with mullite. Calcium is concentrated in the CFB fly ash of 45μm, of which CaO content reaches 615%, while CO content in CFB fly ash greater than 58μm and 4558μm which is about 100%.