The nanostructures of precious metals such as gold, silver and copper all have surface plasmon resonance effects, which have important applications in the fields of surface enhanced Raman scattering (SERS) and photocatalysis. Alloy nanoparticles are expected to have the advantages of multiple metals, giving metal nanoparticles more excellent qualities. In this paper, we have successfully synthesized Au₁Ag₁ and Au₁Cu₁ alloy nanoparticles with the diameter of 1~5 nm by improving the "Brust" method. The prepared alloy nanoparticles have good stability in the air and good solubility in organic solvents. We then assembled Au₁Ag₁ and Au₁Cu₁ alloy SERS substrates by a solution processible method, which shows good SERS performance for 532 nm and 785 nm excitation lasers, respectively. Under the same conditions, the Raman signal intensity of the Au₁Ag₁ substrates to the R6G probe molecule is increased by 2~4 times than that of the Au substrates, showing good SERS activity. The Au₁Cu₁ alloy substrates exhibit stronger photocatalytic activity than the Au₁Ag₁ alloy and Au substrates, and shows potential applications value in the field of photocatalysis.