The hidden presence of fentanyl and new psychoactive substances in established illicit drugs has led to a great number of unintentional fatal overdoses, justifying the urgent need for portable tools for the rapid screening of various drugs. Ion mobility spectrometry, as a rapid detection technique, has been widely used in detecting illicit drugs, whereas it is insufficiently sensitive for bigger ions due to the mobility discrimination of an ion shutter. In this work, a miniaturized ion mobility spectrometer with an inner diameter of 14 mm and a drift length of 38.9 mm and equipped with a novel dual-compression tristate ion shutter has been developed, which could greatly reduce the mobility discrimination by compressing the ion packet twice during the injection process. The best gating performance of the dual-compression tristate ion shutter was about three times as high as that of the tristate ion shutter and twice as high as that of the Tyndall-Powell shutter. For example, the peak height was increased by 150 or 40% when the resolving power was the same, whereas the resolution of two neighboring peaks was improved by 46 or 19% when the peak heights were the same. In screening of fentanyl drug mixtures, the new shutter enhanced the identification accuracy of constituents by making peaks of slow dimer ions and complex ions observable. Besides, the new shutter helped to achieve high sensitivity for drug ions spreading a wide ion mobility range from 0.644 to 2.032 cm2 s-1 V-1, demonstrating its potential use in the analysis of other mixtures and the detection of large ions.