A leak-proof LED (Light Emitting Diode) base structure includes a ceramic substrate and a ceramic reflection ring. The ceramic reflection ring is coupled to the ceramic substrate by a heat-resistant epoxy resin to prevent encapsulant filled in an LED base from flowing out through a junction between the ceramic reflection ring and the ceramic substrate. A groove for receiving an overflow of the heat-resistant epoxy resin is formed on a coupling surface of the ceramic reflection ring. The ceramic reflection ring has a polished reflecting surface for reflecting light emitted by an LED die so as to increase luminosity of the light emitted by the LED. A lens positioning portion is formed on the top of the polished reflecting surface for allowing a lens to be precisely aligned with the ceramic reflection ring, enhancing preciseness of lens assembly, and improving resultant optical configuration of the light emitted by the LED.