The hybrid grid was adopted and numerical prediction analysis of propeller exciting force considering free surface was performed for KCS Hull‐Propeller‐Rudder system by employing RANS method and VOF model .Firstly ,the bare hull resistance ,free surface and propeller open water per‐formance were calculated and calculated results are in good agreement with experimental data ,thus the feasibility of the calculation method could be verified .Then ,the unsteady calculation for KCS Hull‐Propeller‐Rudder system was conducted .And the time domain curves of propeller exciting force were obtained .The frequency spectrum curves were also provided after Fast Fourier Transform .By analyzing the frequency spectrum data ,it is easy to summarize that all kinds of propeller exciting force have the same fluctuation frequency and they all show different degrees of peak in integer times blade frequency .The peak in BFP is maximum and then the peak gradually decays to zero .what's more , fluctuating pressure value in starboard monitoring point is greater than in port monitoring point and it’ value in monitoring point behind propeller is also greater than in front of propeller because of pro‐peller’ right‐handed rotation and wake turbulence .%采用混合网格技术，利用RANS方法和VOF模型，对计及自由液面的KCS船桨舵一体系统开展了螺旋桨激振力数值预报分析．对裸船体阻力、自由液面和螺旋桨敞水性能进行了计算，计算结果与试验值吻合良好，验证了计算方法的可行性．对船桨舵一体系统做非定常计算，得到螺旋桨激振力的时域变化曲线，经快速傅里叶变换得到其频谱曲线．分析得出，螺旋桨各类激振力具有相同的脉动频率，均在整数倍叶频处表现出不同程度的峰值，以叶频处为最大，然后逐渐衰减为0．另外由于螺旋桨的右旋和尾流扰动，使右舷测点脉动压力值要大于左舷测点，桨后测点脉动压力值要大于桨前测点．
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