The invention discloses a method for analyzing the connection direction of the down lead of the grounding grid based on the magnetic field method. The method comprises steps of selecting two down leads to inject and discharge current respectively on the ground surface of a grounding grid branch; taking a to-be-tested down lead as a base point to establish a to-be-tested area A; first determining aconnection mode; then determining the horizontal arrangement direction of the to-be-tested down lead and the connection point of the to-be-tested down lead and the grounding grid branch according tothe measured synthetic magnetic induction intensity and the horizontal magnetic induction intensity of the earth surface; and finally determining the connection direction of the to-be-tested down lead. The method can accurately determine the connection direction of the down lead of the grounding grid, the whole analysis process is simple to operate, and the connection directions of the down lead of different connection modes can be accurately determined, so as to provide the accurate reference basis for topology detection and corrosion diagnosis technology of the grounding grid. The detectionprocess is simple, the amount of data calculation is small, and the analysis efficiency of the connection direction of the down lead is improved.