An electrical connection device and assembly method thereof includes a substrate with a plurality of contacting portions arranged on a surface thereof; a chip module having a plurality of terminals inclining in one direction and compressed and contacted with the contacting portions correspondingly; at least one restricting structure which restricts the chip module to move a distance relative to the substrate depending on the compression deformation of the terminals when the terminals are contacted with the contacting portions; and at least one elastic element just producing deformation when the chip module moves the distance. When the terminals are compressed and contacted with the contacting portions, the restricting structure restricts the chip module to move the distance depending on the compression deformation of the terminals, so that the elastic element just produces deformation, which make the chip module only move in the direction opposite to the deformation direction of the terminals.