This study was aimed to measure the volume of liquid in soft package in a fast and non-invasive manner. Based on the research of theory of Helmholtz resonator, the effect of resonator cavity volume on the acoustic system was analyzed. The Virtual Lab software was used to simulate the measurement system designed, and the relationship between the maximum frequency of transmission loss and the detected volume was obtained. The acoustic testing system for the volume of liquid in soft package was established and the Labview software was applied to acquire the acoustic signals at inlet and outlet of the tunnel. The acoustic decomposition method was used to analyze the signals acquired and the transmission loss of the acoustic system was obtained. The test results indicated that when the volume of liquid in the soft package increased from 25 to 200 mL, and the frequency of maximum transmission loss increased from 256 to 278 Hz. The experiment and the simulation possessed the same trend and the sensitivity of the measuring setup was 7.4 mL/Hz. In conclusion, the acoustic measurement system based on the Helmholtz resonator can be used to measure the volume of liquid in the soft package.