<p>We prepared Co_<i>x</i>Pt_{100−<i>x</i>} (<i>x</i> = 40, 45, 50, 55, 60) nanoparticles by the sol-gel method. The phase composition and crystal structure, morphology and microstructure, and magnetic properties of the samples were characterized and tested using X-ray diffraction (XRD), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM), respectively. The results demonstrate that the coercivity of CoPt nanoparticles can be effectively controlled by adjusting the atomic ratio of Co and Pt in the samples. Among the compositions studied, the Co₄₅Pt₅₅ sample synthesized by the sol-gel method exhibits smaller grain size and a coercivity as high as 6.65×10⁵ A/m is achieved. The morphology and microstructure of the nanoparticles were analyzed by TEM images, indicating that a slight excess of Pt can effectively enhance the coercivity of CoPt nanoparticles.</p>