Abstract: The real-time monitoring and rapid post-earthquake detection of site liquefaction based on strong motion records is a new technological tool for liquefaction mitigation, the core of which is the site liquefaction detection method. The existing methods are constrained by the limited liquefaction site records and the limitations of the methods themselves, and their applicability and detection accuracy need to be improved. In this study, a new database of strong motion records for liquefaction sites containing 137 records from 23 earthquakes is established, which greatly expands the existing database. A new method for rapid detection of site liquefaction based on strong motion records with improved frequency decrease rate is proposed, taking the frequency decrease rate as the basic concept and following the theoretical thresholds derived in the past. The weighted average method is used to process the results of short-time Fourier transform to obtain the time-frequency curve of acceleration time history. The adaptive duration calculation of frequency decrease rate parameter is used to enhance the adaptability to the records of different durations. The comparative analysis based on the new database records shows that the feature parameter selected by the new method is obviously superior, with high detection success rates for both liquefied and non-liquefied sites, and the liquefaction detection success rate is significantly higher than that of the newly proposed methods. The proposed method has good application prospects in rapid detection of liquefied sites after earthquakes, real-time mitigation of liquefaction, and study of liquefaction effects on building structures.