Abstract: According to the power spectral density (PSD) of the horizontal velocity and acceleration process for water mass point, the PSD function of random wave force is derived from the point of view of auto-correlation function for the stationary stochastic process using the linearized Morison equation. Then, based on the original spectral representation for the stationary random process, the standard orthogonal random variable set is defined as the form of orthogonal functions only containing one elementary random variable, which realizes the dimension-reduction simulation of the continuous stochastic wave force field. Meanwhile, combined with the fast Fourier transform (FFT) technology, the fast algorithm of dimension reduction simulation for the continuous stochastic wave force field is given. In the end, the random wave force acting on a small-scale straight cylindrical pile is simulated as an example. This paper provides the numerical characteristics of the method, such as mean, standard deviation, autocorrelation functions and cross-correlation functions, and the calculation results of the proposed method are compared with the Monte Carlo method. The research shows that the proposed method has a higher simulation accuracy and efficiency, which verifies the validity of the proposed method.