A projection display system includes a light source assembly, a wavelength adjusting assembly, and a modulation assembly. The light source assembly is configured to emit projected light. The wavelength adjusting assembly is disposed on an optical path of the projected light for adjusting spectrum of the projected light, and a ratio of luminous efficacy of adjusted projected light to luminous efficacy of monochromatic light corresponding to a dominant wavelength of the projected light is greater than a preset ratio, and color gamut of the adjusted projected light satisfies a preset color gamut coverage. The modulation assembly is disposed on a light exiting path of the wavelength adjusting assembly and configured to modulate light emitted by the wavelength adjusting assembly and output corresponding image light to form projection image.