It is preferable to detect the leakage status at the earliest phase in the manufacturing process, and then, further assembly of hydraulic components with leakage faults can be avoided. Integrating a USB-based microcontroller and a pressure transducer and also with environmental and safety considerations, this study developed a hydraulic leakage detection system by using air in lower-pressure operation ranges, through measuring pressure decay signals captured in real time. Pressure decay data were collected with the developed hydraulic leakage detection system, in which a hydraulic testing tube was installed in tight vs un-tight threading connections to simulate the leakage vs no leakage treatments at two different system pressure levels. Through statistical analysis, it was found that the developed prototype system can capture and visualize the pressure decay curve in real time, and two signals, the pressure drop from the test start to end point and the pressure drop rate in the testing period, can be used as featured characteristics to quickly detect hydraulic leakage components' status.