Micro abrasive air jet (MAAJ) cutting technology is being increasingly used in the precision machining of hard and brittle materials, due to its distinct advantages of negligible heat effect zone and small cutting force. In this paper, an experimental study on the kerf characteristics, especially for the effect of cutting parameters on the top edge definition, is presented. It shows that the top kerf edge is straight but not sharp. The top edge definition of the kerf improves with a decrease in the air pressure, while the effect of abrasive flow rate and nozzle traverse speed are hardly discernible. The optimum jet incidence angle for highest top edge definition of the kerf is 60°. The results of this paper may be useful for the cutting parameters optimization in the precision three-dimensional micro-structural machining.