The invention discloses a piezoelectric impedance-based prefabricated pipe gallery joint water seepage detection method. The method comprises the following steps of: a first stage, pre-testing: arranging a piezoelectric sensor array, establishing a piezoelectric admittance test system, taking a piezoelectric admittance signal as a detection index, and constructing a relational expression between the piezoelectric admittance signal and the water quantity under each level of water quantity; and in the second stage, formal testing: applying a relational expression constructed in the pre-testing stage, performing real-time monitoring for the joint water seepage of the prefabricated pipe gallery structure according to piezoelectric admittance signals. According to the invention, water seepage is detected through adoption of a piezoelectric impedance method, a RMSD index is used for quantitatively describing the water seepage amount, the structure is simple, use is convenient, the detectionreal-time performance is high, and timely overhauling of joint water seepage of the prefabricated pipe gallery structure is facilitated.