A card edge connector includes an insulative housing and a number of terminals retained in the insulative housing. The insulative housing defines a slot going through a front surface thereof to receive an electrical card. Each terminal includes a contacting portion extending into the slot and a tail extending out of the insulating housing. The insulative housing has a retaining wall above the slot. The card edge connector further includes a nut retained in the retaining wall, and cooperating with an external retaining member to fix the heat dissipation module to the insulative housing. The card edge connector can be adapted to expand the module of the existing electrical card to meet diverse needs of customers.