<p>In this study, strain overestimation and stress oscillations in split-Hopkinson tensile bar (SHTB) experiments with clamped flat specimens are investigated. We demonstrate that strain overestimation arises from additional contributions of the transition section, which is initially clamped but pulled out of the fixture during deformation. Besides, stress oscillations originate from impedance mismatch between the bar and the fixture, leading to stress wave reflections and transmissions that superpose and result in oscillations. To address these issues, a geometric strain correction model and a three-impedance model for analyzing oscillations are proposed and validated through finite element (FE) simulations and experiments. The strain correction model quantitatively evaluates the extra strain and subsequently subtracts it. The three-impedance model reveals that stress oscillation can be suppressed by lowering the impedance in the transition region, or even eliminated by applying a low-impedance adhesive between the specimen and the fixture in experiments. However, such oscillation elimination causes serious undermeasurement in the early part of the curve, although the later smoothened part is of adequate accuracy. In order for the entire stress–strain curve to be adequately measured, a compound method is proposed by consolidating the data from the elastic part of the original experimental curve and the following part of the impedance-reduced experimental curve.</p>