According to the energy characteristics of random waves，a method for judging large-scale circular cylinders subjected to random waves is suggested. On this basis，the dimension-reduction simulation method for random wave force field in terms of large scale single circular cylinder and multiple circular cylinders is derived utilizing the power spectral density function of random wave force and the random function-based dimension-reduction idea. Numerical analysis shows that the relative errors of mean，standard deviation，power spectrum，auto-correlation functions and cross-correlation functions generated by the proposed dimension-reduction method are all in good agreement with the corresponding target values. Moreover，comparison indicates that the simulation accuracy of the proposed dimension-reduction method is higher than that of Monte Carlo method，and the simulation efficiency is equivalent to Monte Carlo method. Meanwhile，large-scale circular cylinders are compared and analyzed based on diffraction theory and Morison equation to investigate the errors caused by large-scale cylinders based on Morison equation. Through the comparisons and analysis of the simulation results of cylinder in the case of single cylinder and cylinder group，the influence of cylinder group effect on wave force is explained.