Fluorescent polymer and poly (sodium 4-styrenesulfonate) ionomer (PSS-ionomer) blends were used as emitting layers in polymer light-emitting diodes (LEDs). The two polymers were blended in the optimal ratio which shows the highest luminescent intensity due to dilution effect. We changed the ionic contents of ionomer from 5 mol% to 10 mol% with fixed optimal blended ratio. We obtained the narrow spectrum having high color purity in the blend system. The conjugated polymer/PSS-ionomer blend devices achieved a more enhanced luminescent efficiency as compared with that of the conjugated polymer/PS device due to polar groups in the PSS-ionomer, which enhance the electron injection from the cathode to the emitting molecules.