A light-emitting diode (LED) filament structure includes a substrate, an LED chip unit, a first chromic layer, and a light conversion layer. The LED chip unit is disposed on the substrate, and includes first and second LED chips emitting different excitation lights. The first chromic layer covers the first and second LED chips. The light conversion layer covers the LED chip unit and the first chromic layer. The first chromic layer is configured to transition between an inactivated state and an activated state to prevent or allow the excitation light from the first or second LED chips to pass therethrough, so as to excite the light conversion layer to emit different excited lights having different color temperatures.