Abstract: OBJECTIVE To compare the characteristics of intravascular ultrasound in diverse TCM types of acute coronary syndrome(ACS). METHODS 66 patients diagnosed with ACS via IVUS were divided into group of toxic heat and blood stasis syndrome(NHST group with 36 cases) and the group pf non-toxic heat and blood stasis syndrome(Non-NHST group with 30 cases) based on syndrome differentiation. The indexes such as plaque area in criminal lesions， the area of extra-elasticity membrane(EEM)， plaque burden， the incidence of high risk plaques， the positive or negative remodeling percentage and remodeling index(RI) were measured by IVUS. Analysis was performed by statistical package SPSS11.0， with the data being compared. RESULTS The plaque area in criminal lesions， the area of EEM and plaque burden in NHST group were significantly larger than those in Non-NHST group(P<0.01) respectively. The incidence of high risk plaques and RI in NHST group were markedly higher than those in Non-NHST group(P<0.05) respectively. More positive remodeling was observed in NHST group(P<0.01) while more negative remodeling was seen in Non-NHST group(P<0.01). CONCLUSION The coronary arterial atherosclerotic plaques in patients with NHST maybe more unstable.