The work aims to affirm a type of container's sealing structure which can resist impacting test environment of radioactive material type C packages, so as to provide references and basis for sealing structural design of analogical radioactive material transport containers. The sealing structure of type C package's containers was designed, and a type of feasible sealing structure was determined by numerical analysis. The impacting test was completed to validate availability of such sealing structure. The integral standard leak rates of containers were all smaller than 0.01 mPa•m3/s after angled impact, top down impact and side impact onto an unyielding target at velocities not less than 90 m/s. The sealing structure designed can withstand the impacting test experiment whose impact unyielding target speed is not less than 90 m/s, and can protect radioactive materials effectively.