Abstract: Objective Through a comparative study of ⁹⁹Tc^m-diethylenetriaminepentaacetic acid (⁹⁹Tc^m-DTPA) and ⁹⁹Tc^m-octreotide (⁹⁹Tc^m-OCT) SPECT orbital scan, evaluated the clinic significance of two imaging of estimation activity in thyroid associated ophthalmopathy (TAO). Methods Acording to the clinnic activity score (CAS), 26 TAO patients were divided into two groups:active group (CAS≥3) and inactive group (CAS<3), 14 volunteers (control group) participates this study. Orbit scan were completed after intravenously injection with ⁹⁹Tc^m-DTPA 740 MBq and ⁹⁹Tc^m-OCT (every other day). Obtaining the uptake ratio (UR) of two kinds of orbit scans. The statistical analyses included Paired-samples t test analysis of variance and Spearman regression analysis. Results There is no statistically significance between the two methods in UR (t=0.075, P>0.05). There is a statistically significant correlation was found between CAS and the uptake ratios(⁹⁹Tc^m-DTPA:r=0.835, P<0.001; ⁹⁹Tc^m-OCT:r=0.912, P<0.001). Conclusions There is a good uniformity between ⁹⁹Tc^m-DTPA and ⁹⁹Tc^m-OCT orbital scan; ⁹⁹Tc^m-DTPA is a feasible and maybe a new promising estimation method of activity in the patients with TAO.