The detection of trace trinitrotoluene (TNT) explosives by Surface Enhanced Raman Scattering (SERS) was studied. A novel organic metal framework ZIF-8@Ag composites material prepared by in situ growth was used as SERS substrates. Meanwhile, the structure and properties of the composites were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy(TEM) and X-ray powder diffraction(XRD). Results show that the ZIF-8@Ag composites material has good SERS activity, and the enhancement factor is calculated as 8.84×10³. The probe 4-ATP is self-assembled on the surface of AgNPs. And it could selectively recognize TNT by the interaction of probe 4-ATP and TNT molecules. The detection limit is as low as 10^-9 mol·L^-1. In addition, the mechanism of the interaction between the probe 4-ATP and TNT was studied by ultraviolet spectroscopy, which found that TNT and 4-ATP formed Meisenheimer complex.