The invention discloses a phase noise measuring method based on a wide frequency range, short response time and high resolution. The phase noise measuring method comprises the following steps of: firstly, conditioning and shaping a tested signal and a reference signal respectively, wherein the tested signal is stabilized by the conditioning, and the reference signal is shaped to be a high-frequency pulse suitable for sampling; secondly, carrying out standard phase shifting on the high-frequency reference pulse, and densely sampling the tested signal in a zero passage part by adopting the phase-shifted pulse and an original phase as a clock of an AD (analog-to-digital) converter, then recovering information indicating that the phases are overlapped and the overlapping is subjected to deviation, and controlling and processing the phase detecting information; thirdly, controlling a measuring gate with the processed phase detecting signal which serves as a switching signal, and carrying out high-resolution zero-clearance gating time measurement on phase overlapping points, thus showing the strength of phase noises by the variation of gating time; and fourthly, processing the gating time measuring information to achieve the conversion between the gating time variation and the phase noises, thus displaying a single-side phase noise power spectrum density curve of the tested signal.