Abstract: In order to study the forward measurement principle of scattering measurement, the diffraction model of 1-D periodic rectangular structure was made by rigorous coupled-wave analysis (RCWA) algorithm and programmed by MATLAB. Measurement characteristics of height, linewidth and duty cycle for 1-D periodic structure were thoroughly discussed. In theory, the measurement resolution of linewidth could achieve nanometer level. The results show that RCWA algorithm could achieve accurate and efficient purpose and its good measurement properties for 1-D periodic micro-and nano-structure provide a scientific and feasible basis for scattering measurement.