Quartz bar (or needle) exsolutions from clinopyroxenes are considered as one of the diagnostic indicators in the ultrahigh-pressure metamorphism, and were frequently identified from several UHP metamorphic belts in the world. Exsolutions in omphacites in eclogites from the Chinese Continental Scientific Drilling Project main hole (CCSD-MH) and Pre-pilot 1(CCSD-PP1) were studies by using laserRaman and electron microprobe analysis, and numerous parallel quartz bars (or needles) were found. For comparison, omphacites in CCSD eclogites without any quartz exsolution were also analysed. The results indicate that the omphacites with quartz exsolution is supersilicic. Ultrahigh-pressure experiments shown that part of silica can form octahedral coordination structure, if pressure is high enough. It's proposed that decline of pressure will facilitate quartz exsolution. The peak pressure of UHP metamorphism indicated by quartz exsolutions in the CCSD omphacites is much higher than 2.5GPa, which was estimated by the previous researchers based on facies transformation of quartz-coesite and graphite-diamond, suggests that subuduction depth of the Su-Lu UHP metamorphic belts may be greater than commonly recognized 80~120km.