A LED lamp which could directly replace an ordinary tungsten, halogen, or electricity-saving light bulb includes a filament, a lamp base and a thermally conductive electric insulator. The filament includes at least one AC LED device, and the thermally conductive electric insulator is filled in a cavity of the lamp base to mechanically contact with the filament and an electrode of the lamp base. When the AC LED device is powered on, the thermally conductive electric insulator provides a thermal channel to transfer heat from the filament to the electrode for heat dissipation enhancement. The LED lamp can be directly inserted into an ordinary bulb socket that is generally used in lighting fixtures, without having to modify the system of the lighting fixtures or use an additional adapter.