Synthetic drilling fluid(SDF) is an important kind of working fluids used in the field of exploitation of deepwater oil & gas resource, and its relevant rheological property plays a crucial role for well construction and subsequent production. In this work, a typical SDF employed in B gas fields of South China sea was specially investigated; a set of high temperature high pressure(HTHP) rheological parameters were firstly measured, and then HTHP rheological performance of SDF was entirely analyzed and, meanwhile, general rheological models were established and comparatively examined; finally, a novel HTHP rheological expression with T and P factors was developed to explore its applicability. The results showed that, in the integrated conditions of 60~150 ℃ and 13.8~82.7 MPa, the distribution of low shear stresses obtained at 3~6 r/min is bag-like, and that of middle-high shear stresses tested at 100~600 r/min appears to be sheet-like; T and P display an apparently opposite effect on SDF rheology, and HT effect on SDF rheology can partly be compensated by the HP thickening behavior; the accuracy of general rheolgical models established here varied in the order: Bingham Plastic equation < Power Law equation ? Casson equation < Herschel-Bulkley equation ? Robertson-Stiff equation, wherein Power Law equation was proposed as the general rheological model of SDF, due to its accuracy and simplicity. HTHP viscosity models, μav(T, P) and μpv(T, P), as well as HTHP rheological model, τ(T, P, γ), were established by introducing Arrhenius approximation with T and P factors. The prediction deviations of models were all focused in the range of 3~6 r/min, and the percentages of mean deviation were 0.83%±0.52%, 1.44%±0.53, and 7.57%±7.17%, respectively. The constructed HTHP viscosity and rheological models can meet the applied requirements on site, which will be helpful to offer key data support for control of deepwater drilling.