Abstract: High-capacity cobalt source transport casks are used to transport ⁶⁰Co industrial irradiators. The radioactive contents have special features of high-activity and high residual heat, so only a few countries have design capacity. This is the first design project for the self-reliant design of high-capacity cobalt source transport casks. This paper was devoted to key technology in shielding design of these casks. The MCAM code and MCNP code were used for the calculation of the dose rate level outside the cask and the design -improvement was applied in the cask to meet the requirements in national standard. A series of test proved the casks have ability to transport high-activity sealed sources safely. Calculation results in design are in well concordance with survey results. It demonstrates the rationality and reliability of the methods used in this shielding design. The patent for the design of high-capacity cobalt source transport casks was obtained. Through the design for cobalt source transport casks, a good foundation is laid for the self-reliant design of spent fuel transport cask.