Objective: To prepare Ru(bpy)32+(SiO2@Ru) coated silica nanospheres as electrochemiluminescence (electrogenerated chemiluminescence, ECL) biosensor probe, and evaluate its application value in the detection of the hepatitis C core antigen (HCVcAg). Methods: The water-in-oil(W/O) microemulsion method was employed for one-pot synthesis of SiO2@Ru nanoparticles. The as-synthesized SiO2@Ru nanoparticles has a narrow size distribution, which allowed reproducible loading of Ru(bpy)32+ inside the silica shell and HCVcAg, on the silica surface with glutaraldehyde as linkage. The as-synthesized SiO2@Ru could be used as a lable for ultrasensitive detection of HCVcAg through a sandwich immunoassay process. Results: The calibration range of HCVcAg concentration detection was 1-1 000 fmol/L，the lowest detection limit was 3 fmol/L. Compared with clinical RNA HCV, there was a good correlation, linear correlation coefficient was R2=0.937 9. Conclusion: With high sensitivity and good reproducibility, SiO2@Ru could be used as a label in clinical diagnosis, curative effect evaluation and blood screening of blood center.