One hydraulic pressure generator has been developed with a unique rotating valve and the waveform of generated waves is approximately square-like shape under the low rotating speed. The generated wave has advantages for research in the dynamic characteristics of hydraulic components. The unique rotating valve consists of a rotor and stator which have a number of rectangle grooves precisely milled on the peripheries of the rotor and stator as fluid channels. The rotating rotor alternately switches the fluid channels to open and close state, therefore the waveform is close to square in principle. The pressure transient on the generated wave plays a major role and influences dynamic performances of generated wave. For analyzing the performances of the generator, one sensitivity pressure transducer mounted on the outlet of the generator to measure waveform in time domain. In addition, through Fourier series expansion the spectrum of generated waves clearly indicates the harmonic components of generated waves. Results show the waveform is close to square-like under the low rotating speed in time domain. In the frequency domain, the spectrum of the generated wave demonstrates the bandwidth is abundant. Thus, the generator could be one kind of function generator to performing the calibration of the hydraulic components.