In this work we present an optical laser based method for characterization of periodical microstructure. It allows indirect evaluation of geometrical and optical parameters of periodical microstructures. Proposed method is applicable for optimization and control of technological processes in the cases when traditional measurement techniques are not suitable. The main experimental results are compared with the computer simulations where the standard programs PCGrate-SX6.0 and and GSolver V4.20b were employed. Error of estimation of geometrical parameters of periodical microstructures by comparing theoretical and experimental values of diffraction efficiencies of periodical microstructures is less than 5%.