This study suggests a simple, quick and non-destructive method for investigation of mechanical parameters (dynamic Young’s modulus, dynamic shear modulus and Poisson’s ratio) detection for rectangular plate structures in laminated composites which only utilizes the fundamental resonant frequency in flexural and torsional modes, mass and dimensions of structures. The method is based on the impulse excitation technique (IET) to pick up the fundamental resonant frequency and then the corresponding formulas are applied to evaluate the mechanical parameters. Numerical simulations using finite element method (FEM) and experimental investigations of several cases based on IET are introduced to verify the accuracy of the IET formulas. The results show that the IET is applicable for mechanical parameters identification for laminated composites plates. The method is expected to detect mechanical parameters of other more complicated structures.