A detachable screen guard assembly mounted on a screen frame of a monitor comprising a screen protector and a fastening apparatus. The screen protector is transparent and made of glass, acrylic, or plastic having excellent transparency.The fastening apparatus includes at least one couple of a hooking member and a bracket member. The bracket member is mounted on the screen frame and the hooking member is mounted on the screen protector. The hooking member attaches mechanically to the bracket member. Because the hooking member can be disengaged from the bracket member, the screen protector can be detached from the screen frame to be cleaned or mounted on another monitor that has a bracket member installed.The invention also includes a method for securing a screen protector to a monitor by strapping the screen protector to the monitor support.