Center type permanent magnet of nuclear magnetic resonance logging instrument probe

The invention relates to a medium-duty permanent magnet for the nuclear magnetic resonance logging instrument probe, in particular to a permanent magnet for generating the gradient magnetic field underground, which is arranged on a nuclear magnetic resonance logging instrument. The permanent magnet is characterized in that the permanent magnet is formed by 10 to 50 numbers of small magnetic pillar bodies which are provided with identical cross sections and stuck together with strong adhesive after being radially charged with magnetism; the total length of the small magnetic pillar bodies after being stuck is between 1800 to 2500 mm. The small magnetic pillar bodies are made of ferrite material. Through-holes are arranged at the centers of the small magnetic pillar bodies. The cross section of each small magnetic pillar body is the middle part of the two symmetrical chords of a circle. The outer surfaces of the small magnetic pillar bodies form symmetrical planes. The two symmetrical planes of the small magnet