In a method for manufacturing a high-brightness planar lamp, a reflecting plate is first provided, and several UV light sources are placed on the reflecting plate. Next, liquid macromolecular polymer is uniformly coated on the reflecting plate and the UV light sources, and fluorescent powder is then uniformly coated on the macromolecular polymer. In another method for manufacturing a high brightness planar lamp, a reflecting plate is first provided, and several UV light sources are placed on the reflecting plate. Next, fluorescent powder and liquid macromolecular polymer are mixed up and uniformly coated on the reflecting plate and the UV light sources. A solidification procedure is then performed. The solidification ways of the mixture of fluorescent powder and macromolecular polymer includes solidification by heating and solidification by illumination of UV light.