Studies of floating structures are becoming increasingly important due to their increased application. The hydrodynamic motion response of floating structures must be controlled within a certain range, especially in the resonance region. In this study, a scale model of a circular cylinder having a height of 300 mm, outer diameter 60 mm, natural heave period 0.78 s and a natural pitch period 1.12 s, was designed and analyzed for hydrodynamic load. We compared this model with other models of cylinders with various heave plates systems. In order to find the size effect of the heave plate, two heave plates of 60 and 80 mm in diameter with a thickness of 5 mm. At first, a free decay experiment was carried out to examine the damped heave and pitch period, as well as the hydrodynamic coefficients in the resonance frequency. The motion response was also analyzed to obtain the heave and pitch motion response in a series of regular waves having periods between 0.51 s and 1.24 s. It was observed that the heave plate significantly enhanced the damped heave period, whereas it had a negligible effect on the damped pitch period. Moreover, the peak of heave Response Amplitude Operator (RAO) was observed to be reduced for the heave plate in the resonance region and the peak of heave RAO was shifted to a long period. Furthermore, a comparatively small peak heave RAO was observed in the experiments. It was indicated that pitch motion has an effect on heave motion in the pitch resonance frequency.