At this stage, the aircraft engine material K4169 alloy is difficult to perform at high temperature. Therefore, a new nickel base K4750 is researched by IMR and Jiangsu ToLand Alloy Co. Ltd, which can serve at 750 oC. In order to get excellent properties, the solidification microstructures and elemental microsegregation behavior are researched to provide reliable data of the new alloy. The solidification microstructures and elemental microsegregation behavior of a new Ni-base superalloy K4750 was comparatively investigated by differential thermal analysis (DTA), Thermo-Calc calculation and isothermal solidification quenching (ISQ) experiment. The results of ISQ indicate that the temperature of liquidus and solidus of K4750 alloy was 1350 oC and 1270 oC respectively, and the precipitated temperature of MC carbide was 1320 oC. The temperature of liquidus obtained by DTA and Thermal-Calc was in close agreement with the the result of ISQ, but the temperature of solidus obtained by DTA and Thermal-Calc was 1306 oC and 1296 oC respectively. In the initial stage of the solidification process, the volume fraction of residual liquid decreased sharply. In solidification process within the temperature range of 1310 oC～1290 oC, the residual liquid in the interdendritic region transformed from connected channels to isolated micro-liquid pools. In the last stage of solidification, these isolated micro-liquid pools were quite sluggish and resulted in the formation of porosity. The microsegregation coefficients of W, Fe and Cr were larger than 1, so they were considered to be negative segregation elements and segregate in solid. In contrast, the microsegregation coefficients of Ti, Nb, C and Mo were less than 1, thus they were positive segregation elements and segregated in the liquid.