Compared with the single metal, multi-metallic nanoparticle has excellent localized surface plasmon resonance with a wide spectral range response, which is beneficial to improving both the photoinduced electron transfer efficiency and the effective electron-hole separation. In this work, the urchin-like Au-Ag-Pt-Pd nanoalloy (Au-Ag-Pt-Pd NU) with multiple tentacles is successfully synthesized by the seed growth method and chemical reduction method. And we explore the optical properties of Au-Ag-Pt-Pd NU at different annealing temperatures. The results show that the transient photocurrent intensity of Au-Ag-Pt-Pd NU annealed at 200 ℃ is 1.6 times that of the primitive Au-Ag-Pt-Pd NUs at 808 nm excitation. In addition, the SERS signal intensity of crystal violet (CV) adsorbed on the Au-Ag-Pt-Pd NUs annealed at 200 ℃ is 1.8 times that of the primitive Au-Ag-Pt-Pd NUs at 785 nm excitation. For the Au-Ag-Pt-Pd NUs in this work, the concentration of CV can be detected to be as low as 10^–12 M. Furthermore, the interesting NIR-SERS sensor enables the detection limit of H₂O₂ at low concentration to reach 0.09–1.02 μmol/L. The results show that the obtained nanoalloy has excellent photoelectric response characteristics and high SERS sensitivity due to the synergistic effect of multi-metal. Thus, it possesses great potential for biological NIR detection in the future.