The factors influencing rising delaying time of liquid surface in low pressure casting were investigated by orthogonal testing for hydraulic simulation.It was found that the pressure-applying speed and anti-pressure in mold cavity have significant effects on the delaying time.The rising delaying time of liquid surface increases with the increase of pressure-applying speed and anti-pressure in mold cavity,meanwhile the air-source pressure and the shape of gap in gap gating system slightly affect the delaying time.The delaying time is low at low pressure-applying speed and is lower at high pressure-applying speed in the condition of accelerating and then slowing the speed.