The next generation of large telescope in China will be 30m class. Based on the studies of LAMOST enclosure, we carry on feasibility studies for CFGT enclosure and conclude that the dimension of enclosure will be in the range of 50-60 m. The design should be featured with optimum dome seeing performance, good wind buffet capability and reasonable cost effectiveness. All the structure frames will be made of compact space trusses, optimized in dimension and minimized in cost. Two preliminary plans for enclosure adopting "open-air" and "foldaway" approach are proposed. The folded enclosure located on a large circular air-cushion can rotate to the wind direction and act as wind screen to mitigate the effects of wind-buffeting on the telescope. A new kind of crane-robot crane will be employed into the service of telescope. The enclosure control system based on Fieldbus network controls and monitors all the devices in the enclosure, including robot crane, driving motors and sensors. The sensors send relevant parameters to computer and the computer controls the corresponding devices to ensure better performance of the enclosure. This paper describes the preliminary design for the CFGT enclosure and discusses the possible technologies to build enclosure.