Eclogites and blueschists are exposed mainly as slices or variable tectonic lenses within garnet phengite schists in Habutengsu area, southwestern Tianshan Mountains, Xinjiang. In this paper, petrography, mineralogical chemistry and p-T conditions of the eclogites and blueschists were studied in detail. The eclogites could be divided into four groups, i.e., glaucophane eclogites, paragonite eclogites, epidote eclogites, and glaucophane-garnet amphibolites (retrograde eclogites), whereas blueschists could be divided into three groups, namely glaucophane-bearing garnet-muscovite-albite schists, garnet-muscovite-glaucophane schists and garnet-muscovite-glaucophane-quartz schists. Major mineral assemblages are Grt+Omp+Pg+Ep for the fresh eclogites, Grt+Gln+Amp for the retrograde eclogites, and Grt+Gln+Phe+Pg+Ab+Qtz for the blueschists. Porphyroblastic garnets show perfect prograde zoning, with X_Mn and X_Fe deceasing and X_Mg and X_Ca increasing from the core to the rim, which indicates a process of increasing temperature and prograde metamorphism. According to the paragenetic assemblages of inclusions within garnet as well as in matrix, four stages of metamorphism were recognized, viz., pre-peak lawsonite-blueschist facies metamorphic stage, peak eclogite facies stage (t=543～579℃, p=1.5～1.6 GPa), retrograde epidote-blueschist facies stage (t=～450℃, p<1.0 GPa), and post-peak retrograde blueschist-greenschist facies stage (t<400℃, p<0.5 GPa). The p-T pseudosection calculation shows that the peak metamorphic conditions were 520～550℃ and 1.7～1.9 GPa for the eclogites, and 520～620℃ and 1.7～2.3 GPa for the blueschists, similar to the results of traditional geothermobarometer. Previous researchers reported coesites preserved in some eclogites and country rocks, which suggested that partial eclogites and partial country rocks within the southwestern Tianshan metamorphic belt underwent UHP metamorphism, but this conclusion is inconsistent with the results constrained by the eclogites in this study. The possible reasons might be as follows: ① the eclogites were affected by later thermal events, which led to the partial variation of both minerals and whole rock compositions. On the basis of the changed whole-rock compositions, the traditional thermobarometer Grt-Cpx-Phe and phase equilibrium simulations certainly show relatively low pressure results, and ② not all eclogites from the southwestern Tianshan underwent UHP metamorphism, and HP-UHP eclogites may represent the metabasites subducted to different depths.