The SERS detection of organophosphorus pesticide ethyl paraoxon and organochlorine pesticides r-666 were achieved by the high-density Au-Ag alloy nanourchin as SERS substrate. The Ag nanoparticles were synthesized firstly, then L-dopa was used to reduce the Ag nanoparticles, and ultimately the formation of Au-Ag alloy nanourchin structure. Using this high density tipped structure as the SERS substrate to detect the organophosphorus pesticide ethyl paraoxon and organochlorine pesticides r-666 on the portable Raman spectrometer, and the results showed high sensitivity. Therefore, our platform for the detection of pesticide residues provide a simple, convenient and high sensitivity method.