The invention provides a sampling device and method for the plant balance pressing juice, which is proper for the plant physiology, bionomy and agriculture study. So it is important in using water, fighting drought and breeding of crop. The plant juice sampling device is made up of the high-pressure tank, the tank switch, the manometer, the air inlet controlling valve, the high pressure connecting pipe, the pressure room, the room cover, the sealing collar, the precise manometer, the exhaust controlling valve and vent. In close condition, it give the pressure on the balance pressure at sampling part and keep it by the gas-liquid balancing technology to extract the juice of leaf, tress, stalk and root for test. The merits of it is that the sample is near the real condition, the time is short, the quantity is much, the sampling part is not limited; the precision and quantity are all meet the advance analysis request; also it can detect the water potential of sampling organic.