The three Antarctic Survey Telescopes (AST3) aim to carry out time-domain imaging survey at Dome A, Antarctica, The first of the three telescopes (AST3-1) was successfully deployed in 2012 January. AST3-1 is a 500 mm aperture modified Schmidt telescope with a 680 mm diameter primary mirror. AST3-1 is equipped with a SDSS i filter and a 10k x 10k frame transfer CCD camera, reduced to 5k x 10k by electronic shuttering, resulting in a 4.3 deg(2) field of view. To verify the capability of AST3-1 for a variety of science goals, extensive commissioning was carried out between 2012 March and May. The commissioning included a survey covering 2000 deg(2) as well as the entire Large and Small Magellanic Clouds. Frequent repeated images were made of the centre of the Large Magellanic Cloud, a selected exoplanet transit field, and fields including some Wolf-Rayet stars. Here, we present the data reduction and photometric measurements of the point sources observed by AST3-1. We have achieved a survey depth of 19.3 mag in 60 s exposures with 5 mmag precision in the light curves of bright stars. The facility achieves sub-mmag photometric precision under stable survey conditions, approaching its photon noise limit, These results demonstrate that AST3-1 at Dome A is extraordinarily competitive in time-domain astronomy, including both quick searches for faint transients and the detection of tiny transit signals.