A Doppler coherence imaging spectroscopy diagnostic has been developed on the HL- 2A tokamak for scrape-off-layer impurity plasma flow measurements. Two- dimensional imaging of line-averaged C2+ flow in the high-field-side scrape off layer with time resolution up to 1 ms, has been achieved successfully by this system. The spatial angular resolution in horizontal direction is ~0.023° and the angular resolution in vertical direction is ~0.25°, over a 34° field of view. A delicate calibration system has been utilized to calibrate the group delay and interference fringe pattern to allow the flow measurement error ~±1 km/s. In this paper, the details of optical instrument, calibration system and measurement results of Doppler coherence imaging diagnostic on the HL-2A tokamak are reported. The scrape-off-layer carbon ion flow dynamics are presented during an edge-localized mode crash.