W-Cu composite powders were prepared by ball milling method using quasi-spherical tungsten nanopowders as starting materials, and further used to fabricate W-Cu composites. The sintering behavior of obtained composite powders was investigated and experimental results reveal that composite powders exhibit high sintering activity and nanosized tungsten spheres could effectively suppress the grain growth of prepared W-Cu compacts. Importantly, composite compacts with high hardness of 409 +/- 9 Hv are obtained when sintered at 1200 degrees C for 1.5 h, which could be attributed to the fine grain size and homogeneous constituents distribution of sintered composites. Furthermore, 96.5% of theoretical density (TD) of obtained compacts could be achieved by liquid phase sintering process due to enhanced grain rearrangement. Kinetic analysis indicates that liquid phase diffusion is the dominant mass transfer mechanism during liquid phase sintering. The grain size comparison of products prepared by pure tungsten nanopowders and W-Cu composite powders confirms fine-grained W-Cu composites could be obtained using quasi-spherical tungsten nanopowders. (C) 2018 Elsevier B.V. All rights reserved.