Abstract: MR40 cask is specially used in gripping and transiting radioactive spent filter for water circuit system of AP1000 unit. In the consideration of the gripping object structures and the requirements of operators, a structure designation of one set of equipment was made, which is a lead vessel with a no-power dead-weight mechanical gripping tool with lifting mechanism to fulfill the requirements of gripping and radioactive protection etc., and the relevant radioactive protection and mechanics calculation was done. Finally, all the tests have been passed after the completion of the equipment and the structure designation was proved to fulfill the functioning requirements.