To address the verification requirements for long-term elevated -temperature performance of ceramic matrix thermal protection materials in aerospace vehicles, this study proposes an experimental methodology for elevated-temperature creep testing of ceramic matrix composites (CMCs). This methodology achieves accurate temperature and strain data acquisition during CMCs creep testing under coupled thermomechanical loading through three systematic innovations: (1) development of an alignment-maintaining suspended clamping system, (2) implementation of extensometer-based indirect strain measurement protocols, and (3) thermal field uniformity optimization in high-temperature furnaces. This study establishes a systematic workflow for CMCs creep testing through methodology development addressing specific testing requirements. Experimental validation was conducted using SiC/SiC CMC specimens under 1200 ℃ thermal exposure with sustained 1500-h duration. Throughout testing, stable thermomechanical loading conditions were maintained, accompanied by complete strain data acquisition without significant fluctuation, demonstrating the methodology’s effectiveness in fulfilling prolonged high-temperature creep evaluation requirements for CMCs.