Housing structure for PCI Express expansion electronic boards able to mechanically stabilize said PCI Express expansion electronic boards so as to guarantee the correct functioning, performance and integrity of the electric interconnection between them and the basic electronic board to which they are connected if there are mechanical stresses such as knocks or vibrations, in order to be able to use PCI Express expansion electronic boards in the automotive field, or in scenarios characterized by perturbations of the important mechanical type. The present invention also concerns an assembly method of the housing structure.