Eu3+-doped potassium tungstate phosphor was synthesized by solid-state reactions. The as-produced phosphor was re-fired with a small amount of flux-like alkali carbonates and boron oxide. It was confirmed that the re-firing process containing a flux led to the uniform particle growth with smooth surface and improved Eu3+ distribution at the surface of particles, resulting in the enhanced red emission. The X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS) analyses were used to determine the role of flux in the system.