The invention provides a fixation device for a turbine, including a flange mounted on a housing of the turbine and a nut assembly received in the flange to apply fixation to an component inside the housing. The flange is fixed to the housing by a plurality of first bolts and comprises a central threaded hole. The nut assembly comprises a nut body with a first hole formed along the central axis of the nut body and a plurality of second holes formed around the central axis, and a plurality of second bolts received in the respective second holes. The nut body is formed with thread on its outer circumferential surface and fitted within the central threaded hole of the flange. The second bolts are screwed in the second holes to apply fixation against the component inside the housing of the turbine. The nut assembly further comprises a plurality of sleeves received in the respective second holes, and the plurality of second bolts are received in the respective sleeves. The fixation device in the present invention is able to apply for small and restricted space condition, which makes it possible to position the device very close to the split plane of the turbine. Further, the whole structure of the fixation device is simple with lightweight and easy to assemble with standard tools.