The present disclosure provides a light-emitting device and a manufacturing method thereof, a taillight and a vehicle. The light-emitting device includes at least one light-emitting element located on one side of a backplane, wherein a wavelength of a first light emitted by each light-emitting element is 500 nm to 580 nm; a wavelength conversion layer located on one side of the at least one light-emitting element away from the backplane and configured to emit a second light with a different color from the first light under the excitation of the first light; and a first optical structure located on one side of the wavelength conversion layer away from the backplane, and including one or more optical elements, each of which is configured to focus the second light along a direction perpendicular to the backplane.