Abstract: Additional flux is a novel killing method suitable for deepwater well control. In response to the characteristics of deep water drilling and well control, this paper studies in detail the whole well killing process with additional flux, and deduces the inequality to achieve safe killing operation also. On this basis, objective function and constraint condition are developed, the calculation method of optimal circulation velocity and additional flow rate ratio is obtained with integration of nonlinear programming theory and field case. The paper provides theoretical basis for actual well killing operation of deepwater-well control.