An electrical card edge connector for receiving an electronic card with a bottom notch therein, includes an insulative housing, a plurality of terminals and an alignment key. The housing includes two opposite side walls, a bottom wall and a central slot among the side walls and the bottom wall. The terminals are disposed in the corresponding side walls and extend into the central slot for mating with the electronic card. The alignment key includes a body received within the central slot, a pair of extension sections covering the two side walls, and a pair of securing sections attached to the bottom wall wherein the body is adapted to be received within the bottom notch of the electronic card.