Liquid jet gas pump (LJGP) is device that canrnharness the flow air and water in the vacuum process. This Liquid jet gas pumprnin the working process without use of moving parts so that construction becomesrnsimple and easily obtained in the process of design and installation instrumentrnsetup. In Liquid jet gas pump system consists of main and supporting equipmentrnthat section chamber, nozzle, throat, diffuser, pipe, elbow, tranquilizers tubernand pump. To increase the performance Liquid jet gas pump necessary tornexperiment with modifying some the major equipment that are considered tornaffect the performance Liquid jet gas pump. In these experiments carried outrnmodification namely throat dimensions throat diameter, where one of the mainrnequipment is necessary to get special attention because of throat occur in continuernprocess and laminar flow, before eventually into the diffuser either turbulentrnor laminar. The purpose of research is to improve the performance Liquid jetrngas pump in vacuum process. The research method with experiments involvingrnwater fluid and air in the area ratio of 0.67, throat diameter of 8.7 mm andrnthroat length 39,15mm. The observed data is primary flow or motive flow that isrn6, 7, 8, 9, 10 GPM and secondary flow is 5-30 scfh. While for the water torncirculate fluid Liquid jet gas pump, use of centrifugal pumps. The resultsrnshowed that throat 8,7 mm diameter and 39.15 mm throat length, a phenomenonrnthat occurs is the increased flow rate that causes a decrease in ratio ofrnpressure so the flow rate decreases motive, and while variation the liquidrndischarge can affect the efficiency of the resulting namely, with variations inrndischarge liquid or motive flow (6, 7, 8, 9 and 10 gpm) and the gas dischargernis 0 -30 scfh, it was found the vacuum pressure that is 6 gpm = 94.7025 kPa, 7rngpm = 96.95 kPa, 8 gpm = 93.91 kPa, 9 gpm = 89.67 kPa, 10 gpm = 87.02 kPa whilernthe highest efficiency is obtained in the discharge liquid 6 gpm is equal torn16.82%. Discharge motive of the higher tend to provide better efficiency at allrnlevels of flow ratio.