Abstract: The effects of composition on the precipitation phases in a novel nickel-based superalloy 718Plus were studied using JMatPro. The results show that the solution temperature of δ phase of alloy 718Plus is lower and γ’ phase is higher compared with alloy 718.Interdendritic segregation of Nb, Mo and Ti is severe during the solidification. The increasing of Mo,Cr and Ti content is responsible for the significantly reduction of melting point. The increasing of Nb content leads to higher amount and higher solves temperature of δ phase. The increase of Al and Ti content leads to higher amount and higher solves temperature of γ’ phase. γ/γ ’mismatch decreases dramatically with the increase of Al/Ti.