[en] This paper describes the thermal system analysis performed for the conceptual design of the Compact Ignition Tokamak (CIT). The CIT vacuum vessel and the first wall will be baked at a temperature of 350/degree/C. The maximum fusion power during plasma operation will be 600 MW for 5 seconds at an interval of 1 hour. The coolant during bakeout and operation will be nitrogen or other suitable gas. In order to analyze the above conditions, a thermal system analysis code (THESYS), previously used for design and analysis of the DIII-D tokamak, was modified and improved for application to CIT. THESYS is a 2-D transient thermal analysis code which models components of the first wall of the tokamak, such as limiters and divertors, the vacuum vessel wall, the insulation system, and the coolant loop. Analytical results for the DIII-D tokamak that were obtained with the THESYS codes show good agreement with the observed results. The THESYS codes was used for design and analysis of the CIT vacuum vessel system for bakeout and plasma operation. The results of the bakeout analysis indicate that a bakeout at 350/degree/C is feasible by using hot nitrogen gas. A system analysis was also performed for the double-null plasma divertor operation and shows that 1 hour is sufficient to cool down the vessel between pulses. THESYS could be used for analysis of other devices, such as JET, JT-60, and ITER. 4 refs., 7 figs., 2 tabs