A detection method for improving detection capability of an ion mobility spectrometer to trace explosives; wherein the ion mobility spectrometer comprises a sample receiving device, a drift tube, a gas circuit system, wherein the drift tube is partitioned into an ionization region and a gas drift region by an ion gate, an end of the gas drift region opposite to the ionization region is provided with a detector for detecting ions; the gas circuit system comprises a drying gas circuit, a drift gas circuit, a doping gas circuit and a no-load gas circuit; the drying gas circuit is adapted to provide dried and purified air to the drift gas circuit, the doping gas circuit and the no-load gas circuit respectively; the drift gas circuit is adapted to introduce the dried and purified air as the drift gas flow into the gas drift region from the back end; the doping gas circuit is adapted to provide dopant vapor and be connected with the drying gas circuit, introducing the dopant vapor carried by the dried and purified air into the ionization region; the no-load gas circuit is adapted to introduce the dried and purified air into the ionization region; wherein the detection method comprises: step one: inserting the sample to be detected into the sample receiving device of the ion mobility spectrometer; step two: triggering the operation of spectrum acquisition of the ion mobility spectrometer through the sensor arranged at the sample receiving device, the acquired spectra showing the real-time information of the weak current generated by collision of the ions onto the detector representative of the intensity of the ions and the arrival time of the ions; step three: after step two, when the number of the acquired spectra reaches the information amount required for accurate detection of explosives with high vapor pressure, adding the dopant instantly within the ionization region by controlling the ON/OFF-state of an electromagnetic valve; step four: after step three, when the number of the acquired spectra reaches the information amount required for accurate detection of explosives with low vapor pressure, stopping the acquisition operation, stopping adding the dopant to the ionization region by controlling ON/OFF of the electromagnetic valve, and connecting the drying gas circuit and the no-load gas circuit via an inlet electromagnetic valve; and step five: analyzing all of the acquired spectra to obtain the detection result. step one: inserting the sample to be detected into the sample receiving device of the ion mobility spectrometer; step two: triggering the operation of spectrum acquisition of the ion mobility spectrometer through the sensor arranged at the sample receiving device, the acquired spectra showing the real-time information of the weak current generated by collision of the ions onto the detector representative of the intensity of the ions and the arrival time of the ions; step three: after step two, when the number of the acquired spectra reaches the information amount required for accurate detection of explosives with high vapor pressure, adding the dopant instantly within the ionization region by controlling the ON/OFF-state of an electromagnetic valve; step four: after step three, when the number of the acquired spectra reaches the information amount required for accurate detection of explosives with low vapor pressure, stopping the acquisition operation, stopping adding the dopant to the ionization region by controlling ON/OFF of the electromagnetic valve, and connecting the drying gas circuit and the no-load gas circuit via an inlet electromagnetic valve; and step five: analyzing all of the acquired spectra to obtain the detection result.