Composition segregation can easily occur during the non-equilibrium solidification of SiGe alloys. The non-uniform composition distribution caused by the fiber fabrication process leads to high fiber loss. In this paper， the thermal processing of the SiGe core silica cladding fiber prepared by the assembly of semi-cylindrical Si and Ge rods is conducted using a CO2 laser， and the effects of different thermal processing conditions on the fiber core composition distribution are studied. The experimental results show that continuous Si-rich SiGe alloys can form at edge of laser scanning area along the laser scanning direction， and the closer to the edge， the more uniform the composition distribution of the fiber core is. This study provides a method to fabricate and optimize a SiGe core fiber to achieve uniform composition distribution of the fiber core.