Five representative types of WC-Co powders were selected to clarify the dependence of the structure of sprayed coatings on the structure of powders themselves. The WC-Co coatings were sprayed with the Jet-Kote process and plasma spraying as well. The structure of WC-Co coatings was primarily characterized by X-ray diffraction. The X-ray diffraction patterns of the sprayed coatings were illustrated compared with those of powders, which aims at a better understanding of the structure of thermally sprayed WC-Co coatings. The selected coating was also analysed by differential scanning calorimetry (DSC). The decarburizing process, and the effects of powder structure and spray conditions on the crystal structure of sprayed WC-Co coatings are discussed in detail.