Bletilla striata has been widely used as a valuable hemostatic agent for thousands of years due to the high levels of bioactive constituents it contains. Here, we used a sensitive ultrahigh-performance liquid chromatography-tandem mass spectroscopy (UPLC-MS/MS) method for the simultaneous determination of three major active ingredients of the B. striata extract, namely, α-isobutylmalic acid, gymnoside I, and militarine in rat plasma. The three major active ingredients were determined using the multiple reaction monitoring (MRM) mode at m/z 189 ⟶ 129 for α-isobutylmalic acid, m/z 457.2 ⟶ 285.1 for gymnoside I, m/z 725.3 ⟶ 457.2 for militarine, and m/z 417.0 ⟶ 267.0 for the IS puerarin. All calibration curves showed good linearity (R2 ≥ 0.999) over the concentration range with the lower limit of quantification between 0.015 and 0.029 μg/mL. The relative standard deviations of intraday and interday measurements were less than 15%, and the method was accurate within 93.3–100.4%. The extraction recovery was 92.65–100.98%, and no matrix effect was observed. The results indicated that after oral administration of B. striata in rats, the Tmax of α-isobutylmalic acid was significantly longer than that of gymnoside I and militarine and the mean residence time and area under the curve of α-isobutylmalic acid and gymnoside I in rats were significantly higher than those of militarine. Moreover, the blood concentration-time curve of α-isobutylmalic acid showed double peaks, suggesting that α-isobutylmalic acid could exhibit the phenomenon of enterohepatic circulation or metabolic conversion. We also explored some of the pharmacokinetic characteristics of three ingredients from B. striata extract in vivo, and the data obtained may provide a basis for the further investigation of B. striata.