Backlight source, assembling method thereof and display device

The invention relates to a backlight source, an assembling method thereof and a display device. The backlight source comprises a light source, a wavelength conversion device and a light guide plate, wherein the light source is arranged for emitting light in the first wavelength; the wavelength conversion device is arranged on a light-emitting side of the light source and is arranged for converting the light in the first wavelength after penetrating through the wavelength conversion device into light in the second wavelength; the second wavelength is different from the first wavelength; and the light guide plate is arranged on one side of the wavelength conversion device far away from the light source and is arranged for receiving the light emitted from the wavelength conversion device and then emitting the light. The backlight source disclosed by the invention can greatly increase the color gamut scope of the display device.