The invention discloses a mark point device fixed based on magnetic force, which comprises an identification fixing block, an identification fixing seat, a magnetic force device and a magnetic force adjusting valve sleeve, wherein the identification fixing block is arranged at the bottom of the identification fixing seat, and the identification fixing seat is fixed on a contact net support column or a concrete rod or a steel frame contact net rod through the identification fixing block; the magnetic force device is arranged in the identification fixing seat, and the magnetic force adjusting valve sleeve is sleeved at the periphery of the upper part of the identification fixing seat; and the relative position of the magnetic force device in the identification fixing seat can be changed by rotary adjustment of the magnetic force adjusting valve sleeve, so as to realize change of magnetic force magnitude between the magnetic force device and the identification fixing block. The mark point device is applied to accurate measurement of railway engineering lines, can solve the technical problems of narrow application range, low networking accuracy, multiple styles and non-uniform mounting of the existing mode for positioning railway track measuring mark points, and can realize mark point setting when CP3 track control nets are constructed on new lines or existing lines and when fixed point systems are established.