The invention discloses a magnetic field structure for a magnetic induction gear encoder. The magnetic field structure comprises a gear encoding disc and an inductive head, a sensor and a permanent magnet are installed in the inductive head, the sensor is located right above the tooth top of the gear encoding disc, the axial deviation between the permanent magnet and the center line y of the sensor inside the inductive head is t, the t is smaller than or equal to 5 mm, the radial deviation between the side, with the edge close to the sensor, of the permanent magnet and the center line z of the sensor is h, the h is larger than or equal to -3 mm and smaller than or equal to 3 mm, a skewing angle formed between the end face of the permanent magnet and the xy plane is alpha, the alpha is larger than or equal to -38 degrees and smaller than or equal to 38 degrees, a skewing angle formed between the end face of the permanent magnet and the xz plane is beta, and the beta is larger than or equal to -36 degrees and smaller than or equal to 36 degrees. By means of the magnetic field structure for the magnetic induction gear encoder, the encoder sensitivity is higher, the accuracy can reach the level that the module0.3 can be accurately distinguished, and the tooth distance capable of being distinguished is smaller than or equal to 0.94 mm; compared with an encoder with the same resolution ratio, the size is smaller, the structure is more compact, the externally-expressed magnetism is weaker, scrap iron is not prone to being absorbed, and a scrap iron protection device is avoided.