Abstract: This paper introduces the pneumatic longan core-removing mechanism, based on the process of longan-core removing before the hull is separated from the flesh fruits, which aims at reducing the longan-core removing loss rate. The mechanism adopts air compressor as power to feed fruits and to drive handspike to remove the longan core while the triangular blade cuts and opens longan during feeding. Also the mechanism can be suitable for the longan of different sizes. The correlative factors that influence the loss rate were considered as blade thickness, pneumatic pressure and flowrate. The result of the experiment shows that the triangular blade thickness mandril diameter, pneumatic flowrate and pressure have a crescent influence on longan core-removing loss rate. When triangular blade thickness is fixed at 2.0 mm, mandril diameter at 7.0 mm, pneumatic pressure at 0.55 MPa and flowrate at 6.0 m³/h in the designed prototype, the longan core-removing loss rate achieves the lowest value.