A composite one-dimensional (1D) Ag sinusoidal nanograting aiming at label-free surface enhanced Raman scattering (SERS) detection of TNT with robust and reproducible enhancements is discussed. 1D periodic sinusoidal SiO₂ grating followed by Ag evaporation is proposed for the creation of reproducible and effective SERS substrate based on surface plasmon polaritons (SPPs). The optimal structure of 1D sinusoidal nanograting and its long-range SERS effect are analyzed by using the finite difference time domain (FDTD). Simulation SERS enhancement factor (EF) can be 5 orders of magnitude as possible. This SERS substrate is prepared by the interference photolithography technology, its SERS performance is tested by Rh6G detection experiments, and the actual test EF is about 10⁴. The label-free SERS detection capacity of TNT is demonstrated in the experiment.