The seismic design of nuclear equipment is an important topic in the anti-seismic field of nuclear power plants. In order to achieve the ground motions fitting design of nuclear power plant equipment to meet the requirements of the typical response spectrum (RRS) matching and the standard power spectral density (PSD) envelope, a standard PSD generation method based on the ground motion fitting method for nuclear power plant site design recommended in the 2014 edition of the Standard Review Program (SRP) is proposed, which considers the effects of iteration correlation and random phase spectrum on the iterative convergence efficiency. The method realizes the artificial seismic wave synthesis with RRS matching and standard PSD envelope by controlling the Fourier amplitude in the process of fitting the artificial wave in the traditional frequency domain method, which provides a test basis for the seismic wave of the floor of the nuclear equipment anti-seismic design. The pressure vessel is selected as the prototype for seismic research of nuclear equipment. And the theory that artificial ground motions matching RRS and envelope PSD will stimulate greater response of equipment is verified by the shaking table test comparing the response peak parameters of the specimen and the power spectral density function in response acceleration time history. It shows that the significance of enveloping PSD requirements in the ground motion fitting design, which can be used as a suggested requirement in seismic design process.