Based on wet chemical precipitation and spray drying technology, a Y–Zr-doped W powder was prepared as a precursor material for the preparation of Y–Zr-modified WC-8Co cemented carbides. The Y–Zr-modified WC-8Co hard alloy prepared by low pressure sintering method was used to study the change in the interface structure between the second phase and the substrate. The result showed that in the Y–Zr-doped W powder, the second phase was Y2O3 and ZrO2 particles. The Y2O3 particles had a coherent interface with the W matrix, which was the reason for the formation of intragranular nano second phases in the modified hard alloys. The interface between ZrO2 and W particles exhibited a semi coherent relationship, which was consistent with the interface structure of WC crystals and the second phase at grain boundaries. Some free second phase particles Y2O3 and ZrO2 in the doped powder formed a staggered interface structure in the modified alloy, generating Y–Zr–O solid solutions dispersed in the bonding phase. The performance of Y–Zr-modified WC-8Co hard alloy were superior to pure WC-8Co alloy prepared by the same process. The stable and compatible interface structure between WC grains and the second phase was an effective means to improve the performance of modified WC-8Co cemented carbide.