The three-dimensional self-assembly Eu3+-graphene composite materials are synthesized through a one-pot hydrothermal reaction under 180 ℃. The obtained samples are analyzed through powder X-ray diffraction, scanning electron microscope, and transmission electron microscopy. The results show that each sample has porous structure and no independent Eu3+ agglomerates. Raman spectrum and Fourier transform infrared spectrum analyses indicate Eu3+ is well complexed with graphene through oxygen-containing groups. The magnetic properties are measured using vibrating sample magnetometer. The magnetic hysteresis loop shows the corresponding coercivity Hc ≈ 39.61 Oe (1 Oe=79.5775 A/m) and the magnetization saturation Ms ≈ 0.08 emu/g that indicates that the sample presents weak ferromagnetism and good soft magnetic properties compared with graphene.