A method for fabricating a self-aligned bipolar transistor, wherein a substrate having an epitaxial layer formed thereon as a base is provided. After this, a first dielectric layer, a second dielectric layer are sequentially formed on the epitaxial layer, followed by forming an opening in the second dielectric layer. A conductive spacer is formed on the sidewall of the opening. Using the second dielectric layer and the conductive spacer as a mask, a first dielectric layer in the opening is removed. A conductive layer is then formed in the opening as an emitter, followed by completely removing the second dielectric layer. A doping is conducted on the emitter. Using the emitter and the conductive spacer as a mask, a part of the first dielectric layer is removed. Further using the emitter and the conductive spacer as a mask, another doping is conducted to form a part of the epitaxial layer as a base contact region.