Observations of 43 GHz v = 1, J = 1−0 SiO masers in the circumstellar envelope of the M-type semi-regular variable star AH Sco were performed with the Very Long Baseline Array (VLBA) at 2 epochs in March 2004. These high-resolution VLBA images reveal that the distribution of SiO masers is roughly on a persistent elliptical ring with the lengths of the major and minor axes of about 18.5 and 15.8 mas, respectively, along a position angle of 150°. The 3-dimensional kinematics model-fitting for proper motions and spatial distributions of maser features clearly indicates that the SiO maser shell around AH Sco was undergoing an overall contraction to the star at a velocity of 15 km s−1 at a distance of 2.26 kpc to AH Sco due to the gravitation of the central star.
