Owing to its long cycle life, high energy density, low self-discharge performance, good thermal stability, and insignificant memory effect, lithium-ion battery (LIB) has attracted research attention as one of the most promising energy storage devices. In this study, as LIB anode materials, polyacrylic acid (PAA)-modified Fe3O4@C core–shell microspheres were synthesized by a hydrothermal method using glucose as the carbon source, and their electrochemical properties were investigated. As-obtained samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy, thermal gravimetric differential thermal analysis (TGA–DTA), and Fourier transform infrared spectroscopy (FT-IR). The electrochemical performance was investigated, including cyclic voltammetry performance, cycle life, rate performance, charge-discharge cycles, and impedance curve fitting. The PAA-modified Fe3O4@C core–shell structure was successfully prepared. Uniform microspheres with a particle size of ~310 nm were obtained, in addition to a uniformly coated carbon layer with a thickness of ~30 nm. In addition, the Fe3O4@C core–shell structure effectively relieved the volume expansion during constant current charge and discharge cycles and prevented the rapid collapse of the crystal structure. A large number of carboxyl groups in PAA exhibited a surface modification effect on Fe3O4, effectively preventing particle agglomeration and ensuring good dispersibility. The effective carbon coating can improve the electrochemical performance of Fe3O4 as the anode material of LIB. The enhanced ionic and electronic conductivities were beneficial for its specific capacity, coulombic efficiency, and cycle stability. Moreover, the Fe3O4@C core–shell microspheres maintained a specific capacity of 655 mAh/g after a constant current charge and discharge cycle of 370 cycles at a current density of 100 mA/g; hence, Fe3O4@C core–shell microspheres can be considered as good candidates for application as LIB anode materials.