Abstract: In the process of solid phase carburization of the reduced W-Co composite powder recycled by co-precipitation was converted from Co₃W and Co₇W₆ to η type carbides at low temperature and was converted from η type to co-grown β-Co and coarse WC crystals at high temperature (over 900℃), the coarse WC crystals were the cause of the formation of super coase. WC crystals in the alloys produced by these recycled materials. Fine WC crystals (<0. 2μm) were directly formed from W and C at 600~1100℃ and produced from W₂C and C at 750~1100℃. There was no catalytical effect of free Co phase on carburization at low temperature. The carburization process could not be completed even if at 1200℃.