The target box is designed to protect the body of divertor cassette. Every new EAST divertor cassette has two target boxes covering its body. The paper is about the structure design and optimizing scheme of the outer/inner tokamak divertor target box. The preliminary structure of target box is built up firstly. And the distribution of thermal load on the target boxes is discussed based on the theory and experiment results of plasma. Then some parameters of the target box’s structure, such as cooling tube radius, cooling water flow velocity and the length between two cooling tube, are selected to discuss the range of values’ limits. Based on the above results, a series of thermal simulations are made through changing the structure parameter values. Finally, using these simulation results the optimal design parameters set are found out.