  CEPC will use 650 MHz cavities for the collider. Each collider cryomodule
contains six 650 MHz 2-cell cavities, which is totally new. Therefore, new
helium vessel and tuner are designed for the 650 MHz 2-cell cavity. Also, a
test cryomodule, which consists of two 650 MHz 2-cell cavities, has begun as
the first step to the full scale cryomodule. This paper mainly focuses on the
structure design of Helium vessel and tuner for the 2-cell cavity.
