A glass stem for a highly waterproof LED filament lamp comprises an LED filament, a glass flare tube, an exhaust tube, a first lead wire having a resistance element, and a second lead wire. The first lead wire is placed in the middle of the exhaust tube. The first lead wire, the second lead wire, the top of the exhaust tube and the top of the glass flare tube are fusion-bonded together. A lower section of the exhaust tube is fused and cut off to an assembly-desired length and then fusion-sealed with the first lead wire to form a glass stem with the resistance element sealed in the middle of the exhaust tube. The first lead wire having the resistance element is disposed inside the exhaust tube, such that isolative insulation is generated between the first lead wire and a second lead wire.