Abstract: The vacuum outgassing of materials is a critical concern of fusion devices. In order to study the outgassing characteristics of large-scale components in the actual operational environment of the fusion device, an outgassing rate measuring device was designed and developed based on the symmetrical structure constant conductance method, which can simulate the baking conditions of the fusion device and the measuring range covers (10⁻⁵~10⁻⁹) Pa·m³·s⁻¹. Moreover, thermal analysis simulations were conducted to verify the heating and cooling system of the sample chamber, ensuring that the components can replicate the temperature increase experienced during baking in a tokamak vacuum chamber for their outgassing testing. The size of the sample chamber is φ500 mm × 600 mm, and the main structure material is SUS316L, with the inner surface treated by ultra-high vacuum technology. The sample chamber achieves heating within the range of 25℃ to 300℃ using a combined heating mode, incorporating a heating platform and the outer wall of the vacuum chamber. A water-cooling module is designed on the exterior of the sample chamber insulation to ensure cooling efficiency and personnel contact safety. The thermal simulation analysis of the baking and cooling module of the sample chamber indicates that the heat insulation layer effectively preserves and insulates heat, with a temperature difference of nearly 150℃ between the inner and outer layers. The water-cooling system provides a significant cooling effect, ensuring that the temperature of the outermost area touched by personnel remains below 55℃. The preliminary test indicates that the device can achieve stable and controllable baking performance, and the analysis of device background outgassing reveals its effective and clean operation, meeting the outgassing test requirements for specialized fusion device components.