InSb is an important material for medium wave infrared detectors. To meet the development requirements of larger format high quality infrared focal plane array detectors, the growth of InSb single crystals with diameter of 100 mm and low dislocation density is studied. By improving and optimizing the growth method, seed, necking process and thermal field, a large size low dislocation density InSb crystal with its dislocation density equal to or less than 100 cm-2 and diameter equal to or greater than 100 mm is obtained eventually. The dislocation density of the crystal is distributed uniformly from the top to the end along the crystal rod. It can satisfy the use requirements of large format high quality infrared focal plane array detectors.