The invention discloses a method for observing roadbed cross section settlement through magnet ring positioning, which is characterized by comprising the following steps of: A. transversally digging a groove in a roadbed; B. installing positioning magnet rings at intervals on the periphery of a section settlement pipe, and then connecting the section settlement pipe by segments and horizontally placing into the groove; C. folding a flexible steel pipe and placing into the groove, enabling two ends of a pulling rope to be positioned at the same side of the roadbed, and then landfilling by using medium coarse sand; D. fixing a section settlement meter with a magnetic field induction buzzer on the pulling rope; E. pulling the pulling rope to enable the section settlement meter with the magnetic field induction buzzer to move in the section settlement pipe, and every time when the magnetic field induction buzzer makes a buzz because the section settlement meter reaches at the position of the positioning magnet ring, recording the reading of the meter in every magnet ring position; and F. carrying out subtraction on observation data obtained in two times to obtain the settlement in themagnet ring position, thereby finishing observation on the roadbed settlement. By using the method disclosed by the invention, the observation precision and the convenience for observation operation are improved greatly.