Gun Shot residues (GSR) are important physical evidence because of their potential, wide distribution and difficulty in destruction. To overcome the disadvantages of traditional detection methods, such as time-consuming, relying on large instruments and weak intuition, Ga/Eu³⁺/DPA rare earth complex probes were synthesized for quantitative detection of Cu²⁺ in shooting residues by hydrothermal method. The morphological size, molecular structure and fluorescence properties of the probes were characterized by transmission electron microscopy, infrared spectroscopy and fluorescence spectroscopy. Then, the synthesis conditions were optimized, and the anti-ion interference capability was investigated. After that, the linear relationship between fluorescence intensity and Cu²⁺ concentration was investigated. Finally, according to the relationship between the concentration of Cu²⁺ in the shooting residue and the distance of bullet holes detected by ICP-MS, the experiment verified that the fluorescent probe is fully capable of quantitative detection of Cu²⁺ in the shooting residue, and is expected to play an important role in the application of criminal technology.