A memory module, comprising: an upper module including a fixed block , a pressure tongue and a reset spring , wherein the pressure tongue is rotatably mounted on the fixed block by the reset spring , wherein the reset spring provides a first driving force for the rotation of the pressure tongue , wherein the fixed block has a downwardly extending upper retaining point , and wherein the pressure tongue has an upper retaining surface formed by its front surface; a lower module engaged with the upper module and including a guide rail , a slider , a rotating block and a torsion spring , wherein the rotating block is rotatably mounted on the slider by the torsion spring , wherein the torsion spring provides a second driving force for the rotation of the rotating block , wherein the slider is slidably mounted on the guide rail , wherein the guide rail has locking holes , wherein the rotating block has a locking block , wherein the slider has an upwardly extending first lower retaining point at its front end, wherein the rotating block has an upwardly extending second lower retaining point at its rear end for engaging with the upper retaining point ; when the front end of the rotating block is raised under the action of the second driving force, the locking block is inserted into the locking hole , and the upper retaining surface is separated from the first lower retaining point ; when the rear end of the rotating block is raised since the rotating block is pressed by the pressure tongue under the action of the first driving force overcoming the second driving force, the locking block is separated from the locking hole , and the upper retaining surface is engaged with the first lower retaining point . an upper module including a fixed block , a pressure tongue and a reset spring , wherein the pressure tongue is rotatably mounted on the fixed block by the reset spring , wherein the reset spring provides a first driving force for the rotation of the pressure tongue , wherein the fixed block has a downwardly extending upper retaining point , and wherein the pressure tongue has an upper retaining surface formed by its front surface; a lower module engaged with the upper module and including a guide rail , a slider , a rotating block and a torsion spring , wherein the rotating block is rotatably mounted on the slider by the torsion spring , wherein the torsion spring provides a second driving force for the rotation of the rotating block , wherein the slider is slidably mounted on the guide rail , wherein the guide rail has locking holes , wherein the rotating block has a locking block , wherein the slider has an upwardly extending first lower retaining point at its front end, wherein the rotating block has an upwardly extending second lower retaining point at its rear end for engaging with the upper retaining point ; when the front end of the rotating block is raised under the action of the second driving force, the locking block is inserted into the locking hole , and the upper retaining surface is separated from the first lower retaining point ; when the rear end of the rotating block is raised since the rotating block is pressed by the pressure tongue under the action of the first driving force overcoming the second driving force, the locking block is separated from the locking hole , and the upper retaining surface is engaged with the first lower retaining point . <EOS>