Taking the Datong-to-Huangshui River Water Diversion Project as the research object, MIDAS GTS was adopted for the simulation of the diversion tunnel using orthogonal design, based on the construction technique and site conditions. Nine different working conditions with the primary support thickness (A), the interval between steel arches (B) and the excavation length per cycle (C) as the influencing factors were simulated to analyze the significance of each influencing factor using extreme range method. Then, in order to achieve the goal of safe construction with less investment, the linear relationship between safety and economy of the construction was analyzed by grey relational theory with the crown settlement, floor uplift and other parameters as the evaluation indicators. Finally, the nine working conditions were analyzed and an optimal construction plan for the tunnel was determined. The results show that the order of the primary and secondary influencing factors of the primary support arch stress was B, A, C, namely the interval between steel arches, primary support thickness and excavation length per cycle, that of the crown settlement, proportion of expenses of excavation and steel arches was C, B, A, and that of the floor uplift, horizontal convergence primary support floor stree, side wall stress and vault foot stress was C, A, B. The proportion of excavation expense and total cost are all negatively correlated with displacement, primary support stress except the proportion of excavation expense relative to vault stress and comprehensive score; whereas the proportion of steel arch expense is positively correlated with the above parameters except the vault stress of the primary support stress. According to the calculation of the grey relational degree of each working condition, it is concluded that the optimal scheme in terms of comprehensive safety and economy is working condition 7, and its relational degree is 0.763. The specific parameters of the primary support thickness is 16 cm, the interval between steel arches is 1.0 m, and the excavation length per cycle is 1.5 m.