In order to control WC grain size and get a microstructure with fine grain size during the sintering process, WC grain growth in WC-Co cemented carbide was investigated. The possible reason on the grain growth was showed which includes the normal grain growth (NGG) and the abnormal grain growth (AGG). We adopted the SPS (spark plasma sintering) to sinter nanometer WC-Co powder, the range of temperature was 1100 -1250 °C, the pressure was 40MPa, and sintering time was 5min. In this paper, we discuss the density, hardness, microstructures and grain sizes of the sintered samples. The results showed that during the process sintering WC-Co powder, there are two kinds of growths. XRD investigation of the WC–Co samples spark plasma sintered to full density revealed that no new phase was created. Through the observed microstructure of the sintered samples, we analyzed the reason of the abnormal grain growth of WC grain. The density and hardness of samples were increased with increasing temperature.