Ship motion responses and added resistance in waves have been predicted by a wide variety of computational tools including potential and viscous flow methods. However, to validate the computational flow field is still challenging. In the present work, ship vertical motions, added resistance and detailed wake flow field for a 3.2m KRISO container ship (KCS) model in waves have been predicted by simulation and experiment. The force, motions and S-PIV measurement were conducted in towing tank using same ship model. The viscous flow simulation was performed by CFDSHIP-Iowa with rigid body motion solver and dynamic overset grid. The ship heave and pitch motions were considered in wave and in calm water. The current result shows good agreement between simulation and experiment for the trend of the motion responses and added resistance. As wave length increases, heave and pitch motion amplitudes increase from near zero to almost constant one but the added resistance coefficient raises until the peak at λ/L=1.15. For the nominal wake at propeller plane, the velocity distribution pattern in short waves, e.g. λ/L=0.65, is similar with the calm water one. In long waves such as λ/L=1.15, the bilge vortex moves up and down relative to the stern vertical motions and remains always inside the propeller radius. The secondary vortex is shedding above and below the dummy boss inside the low speed area. The oscillation of nominal wake factor in waves is almost sinusoidal unlike the KVLCC2 one analyzed in our previous study.