The invention provides a purely-yellow LED lamp for a superclean room, and a preparation method for the purely-yellow LED lamp. The purely-yellow LED lamp comprises a support, an LED chip bonded on the support, heat-conducting adhesive playing a role in die bonding, a fluorescent powder layer coating the LED chip, a filling silica gel packaging layer coating the fluorescent powder layer, and a plastic lens which wraps the filling silica gel packaging layer and achieves the light distribution. The support is welded on an aluminum substrate, and the aluminum substrate is provided with a copper foil circuit in an etching manner. The copper foil circuit is led to the outside, and a semi-cylindrical frosted glass cover on the aluminum substrate surrounds a light source. Because yellow and orange fluorescent powder with a certain concentration is employed, purely yellow light which does not contain blue light is obtained, and the light efficiency is remarkably improved, so the purely-yellow LED lamp is suitable for the superclean room.