ProCAST software was used to simulate the casting of fine grain blisk by thermal controlled. Traditional Udimet720Li deformed superalloy was used as the casting material of blisk to simulate the solidification process, porosity distribution, stress distribution and grain growth of blisk. The solidification behavior and microstructure characteristics of the high γ" superalloy used in fine grain blisk casting were studied. The solidification of the blisk begins at the blade tip and ends at the center of riser. The porosity of the main area of the blisk is 1.5%~3%. In the solidification process, due to the shrinkage and segregation, some areas will form relatively large porosity areas. A safety threshold of 13 (K·Sec)0.5/cm was established to evaluate the feasibility of casting process parameters. The maximum shear stress, effective plastic strain and hot crack index at each position of the blisk are 0, but the effective stress is more than 1200 MPa in the blade tip and edge corner area. The average grain diameter of the blisk is 0.88 mm, which meets the requirement of thermal control method. However, thermal control method is not easy to control the uniformity of grain size, so it should be combined with kinetic method to improve the uniformity of grain size.