The current study was conducted to investigate the potential of three circulating miRNAs (miR-21, miR-16 and miR-100) as HCC diagnostic marker in the population living in Guangdong province, China. First, the Fe₃O₄ and Fe₃O₄@SiO₂ magnetic microsphere were prepared. Fe₃O₄@SiO₂ microspheres were further used for total RNA purification from serum. After that, the real-time qPCR was conducted for the detecting the miRNA in the serum of HCC patients and healthy volunteers. Scanning electron microscope and transmission electron microscope images showed that monodisperse Fe₃O₄ and Fe₃O₄@SiO₂ microspheres were successfully synthesized with a mean diameter of about 500 nm and 600 nm, respectively. The microsphere was spherical in shape with good state of dispersion. The characteristic peak at 1088.8 cm-1 in FTIR spectra belonged to the asymmetry stretching vibration of Si-O-Si, which confirmed the SiO₂ coating on Fe₃O₄ microspheres. The successful amplification of miRNAs in qPCR verified that the total RNA extracted using the Fe₃O₄@SiO₂ microspheres retained high quality. The real time PCR results showed that miR-21 was differentially expressed in the serum of HCC patients and healthy volunteers. miR-21 and alpha-fetoprotein (AFP) together could be potentially used as HCC diagnostic marker in Guangdong province population in China.