Drift tube is an important part of ion mobility spectrometer (IMS). Ions generated in the ion source pass through the drift tube and are separate based on their size and mass. Although, based on "the charge conservation law", the number of ions must remain unchanged, all the ions entering the drift tube do not exit from the other end. In another word, some of the ions are lost along the way. The loss of ions occurs through the collision with the metal wall of the drift tube and hence discharging. In previous work, the percentage of the ion passage, the ratio of output ion to input, was investigated. In this thesis, the ion lost along the drift tube has been studied in detail. The ion current leak through each ring was measured individually and it was shown that the ion losing process exponentially reduces, so that the logarithmic diagram of the ion lost is a linear function of the distance in the drift tube. Therefore, the ion losing is a first-order process. Since the field at the two ends of the drift tube is not uniform, due to the presence of the corona discharge needle and the aperture grid, respectively, breaks are observed in the decreasing ion lost curve. The results are in agreement with the model presented by Kirk et al., A Simple Analytical Model for Predicting the Detectable Ion Current in Ion Mobility Spectrometry Using Corona Discharge Ionization Sources, J. Am. Soc. Mass Spectrom. (2018). Vol.29.pp.1425-1430 . In this model, the ions are assumed to enter the drift tube as a cone shower and expanding as they proceed. Hence, the ions less likely hit the first ring. The angle and the base of this cone shower are a function of the drift field and the corona current. According to this model, the ion current reached the collector is not a function of the ion current generated by the corona discharge. The experimental results perfectly match the theoretical prediction.