Super GH4738 superalloy has been chosen as a candidate alloy used for oversized turbine disc in gas turbine field. Thermo-Calc and JMatPro softwares were used to optimize composition of alloy combined with experiments. The effects of elements C, Al, Ti and Cr on phase precipitation and mechanical properties were calculated. Based on the calculated results, Several GH4738 superalloys with different contents of Al, Ti were melted and examined by tensile strength properties at room temperature and the final elements of super GH4738 superalloy were determined and its phases analysis were carried out. The results showed that increasing of C content can promote an increase of carbides( M₂₃C₆ and MC) and solution temperature, but it has almost no effect on the changes of γ￠ phase amount. Elements Al, Ti can significantly increase solution temperature and its amount for γ￠ phase and improve strength of GH4738 alloy. Solution temperature γ￠ phase would increase with increasing of element Cr, while almost no influence on precipitating γ￠ phase. The influence degree on solution temperature and amounts γ￠ phase for element were Al>Ti>Cr. The design principles of GH4738 super alloy was to reduce the C content, and improve Al, Ti content to the upper limit in the range of the alloy. The amount of super GH4738 alloy was about 24.0%, its lattice constant a₀=0.357-0.359 nm, its composition (Ni_0.9236Co_0.0415Fe_0.0025Cr_0.0322)₃ (Cr_0.0972Al_0.3585Ti_0.5059Mo_0.0366Cr_0.0018). The results would provide a guideline and design idea for large higher strength GH4738 superalloy turbine disk.