A loading test of the ground settlement (GS) performance of the oil tank must be examined before beginning its commercial service. This test requires the sensors to be installed around the oil tank, and the GS is measured while water is being filled in, where the liquid level is read with an ultrasonic radar equipment, etc., to indicate the applied water loads. During the service of the oil tank, loading and unloading corresponding to the oil inlet and outlet are the critical factors to cause the oil tank destruction in a fatigue way. Thus, a regular in-service loading test is the means of evaluating the tank base health condition. However, the sensors for GS measurement of the oil tank are mostly based on a liquid hydraulic sensor, which is an intrinsically static sensor determined by the fluidity of the measurement liquid. In order to meet the instantaneous requirement of the loading test, first, the configuration of the optical GS sensor was designed to suit the simultaneous measurement. Secondly, a data acquisition system was designed by combining the digital signal processing with a field programmable gate array to carry out a parallel multiple channel data collection. This ensures that the GS sensors are interrogated simultaneously to snapshot a GS status of the oil tank, even if its load was changed slowly. A practical oil inlet process was recorded with an ultrasonic radar oil level measurement, and the results of oil tank GS were verified with a manual measurement by using the Electronic Total Station. The effectiveness of our sensor monitoring of the oil tank GS performance during the loading test has been proven.