A 100MeV compact high intensity H-cyclotron is under design and construction at CIAE which will provide a 75MeV—100MeV,200μA proton beam.The main magnet of this cyclotron adopts an integrally compact structure with a fixed field and four sectors,while the hill gap is constantly changeable.This paper reviews the design features of the magnet,numerical simulation results,the inner defects of the magnet including the carbon content segregation and shrinkage porosity,factors related to mechanical design including the tolerance and deformation.The latest progress will also be reported in this paper.