Abstract: To enhance the activity of WC powders, the one-step activation method was applied, followed by the electroless plating process, for fabrication of the Co-coated WC composite powder. The effects of the HNO₃: HF ratio on the micro-defects activated sites on the surface of WC, the growth of Co coating, and the microstructure and mechanical properties of cemented carbide were investigated. It was found that, when the activation solution with lower ratio (2: 4) was used. the oxidation reaction of HNO₃ was limited, the micro defects on the WC surface were limited due to the poor activity of the WC. When the ratio of activated solution increased to 3: 4, and 4: 4, the activity of WC increased gradually. When HNO₃: HF=5: 4, a large number of stepped defects were formed on the surface of WC activated powders, which provided sufficient active sites for the uniform growth of Co coating. Under this condition, cemented carbide with uniform microstructure was obtain, and the hardness reaches 2109.6HV30 and fracture toughness reaches 10.48MPa·m ¹^/². The high ratio of activation solution (6: 4) leads to over corrosion, which inhibited the composition uniformity of WC-Co composite powders and further posed bad influence to the microstructure and mechanical properties of the cemented carbide. In this study, the influence of the ratio of activation solution on the activity of WC powder was clarified, and the optimal ratio of HNO₃: HF=5: 4 was obtained. In this study, the influence of the ratio of activation solution on the activity of WC powder was clarified, which would guide the fabrication of high-quality WC-Co powders.