SiC/SiC composite is a promising candidate functional and structural material for fusion reactor system.The Nano-Infiltration and Transient Eutectic-phase(NITE)method is one of the most attractive process for SiC/SiC composites fabrication because of its advantages in formation of high density SiC matrix,size and shape flexibility and cost efficiency,which is an advanced liquid phase sintering method.Currently,R & Ds of NITE method toward industrialization are on-going at OASIS,Muroan Institute of Technology.The NITE process for industrialization is called “DEMO-NITE” process,which utilizes dry type inter-mediate materials.In order to apply SiC/SiC composites by DEMO-NITE process to fusion reactor components,it is important to understand thermal properties such as mechanical properties and thermal conductivity in high temperature.However,thermal properties evaluation of DEMO-NITE-SiC/SiC composites is not sufficient yet.The objective of this study is to evaluate stability of mechanical properties of DEMO-NITE-SiC/SiC composites in high temperature.This paper is provides mechanical properties of DEMO-NITE-SiC/SiC composites after high temperature exposure under low oxygen partial pressure.The potential application to fusion reactor of DEMO-NITE-SiC/SiC composites will be also proposed.