Two improvements have been made to Rouard′s method for the analysis of fiber and waveguide gratings. The element of reflection is chosen to be a section of half period instead of a period, and the real reflectivity of each interface is used instead of an approximate value obtained by coupled mode theory. The improved Rouard′s method becomes a complete Rouard′s method with higher accuracy. It is simple and independent on coupled mode theory for no calculation of the coupling coefficient required. Numerical examples of uniform and nonuniform gratings are given.