<p>The exploitation of a bifunctional material for both identifying and extracting heavy metal ions (HMIs) is essential but still poses a major hurdle. In this work, a novel magnetic fluorescent nanocomposite (Fe₃O₄/CD@SiO₂-QD) was successfully prepared for the specific detection and removal of Cu²⁺. Magnetic fluorescent nanoparticles (Fe₃O₄/CDs) exhibiting blue fluorescence were synthesized via a one-step hydrothermal approach, and a magnetic ratiometric fluorescence sensor was prepared after SiO₂ and red fluorescent CdTe quantum dots were coated on the surface. When Cu²⁺ is present in the solution, the red fluorescence of the magnetic ratiometric fluorescence sensor is quenched, and the blue fluorescence remains essentially unchanged, resulting in a ratiometric fluorescence effect, which can be used for the sensitive determination of Cu²⁺; the magnetism can be used concurrently for the removal of Cu²⁺ to achieve detection and removal, and the detection results exhibit good linearity within the 2.5–100&#xa0;μM range, with a limit of detection of 0.23&#xa0;μM. This method was used for the spiked determination of copper ions in actual samples, with recoveries ranging from 93.02 to 107.31%. In addition, the sensor effectively removes Cu²⁺, and each gram of magnetic ratiometric fluorescence sensor can remove up to 72&#xa0;mg of copper ions. Therefore, our prepared magnetic fluorescence sensor can introduce an innovative strategy for the determination and removal of copper ions in environmental or biological samples.</p>