In this work, the experimental value of the hydrodynamic forces acting on two different types of the floating offshore structure were obtained by the excited method by the transient water waves. Another object of this paper is to check the reliability of the new developed program that calculate the motions and hydrodynamic forces of the offshore structure. Therefore, the comparison between the experimental and calculating values of the wave exciting forces, added masses, damping coefficients and motions in waves are presented. Consequently, both of the calculating values by the new program and the estimating values from the experimental hydrodynamic coefficients were coincident with the experimental values of motions in waves.