Triacetone triperoxide (TATP) is a self-made explosive synthesized from the commonly used chemical acetone (C3H6O) and hydrogen peroxide (H2O2). As C3H6O and H2O2 are the precursors of TATP, their detection is very important due to the high risk of the presence of TATP. In order to detect the precursors of TATP effectively, hierarchical molybdenum disulfide/reduced graphene oxide (MoS2/RGO) composites were synthesized by a hydrothermal method, using two-dimensional reduced graphene oxide (RGO) as template. The effects of the ratio of RGO to raw materials for the synthesis of MoS2 on the morphology, structure, and gas sensing properties of the MoS2/RGO composites were studied. It was found that after optimization, the response to 50 ppm of H2O2 vapor was increased from 29.0% to 373.1%, achieving an increase of about 12 times. Meanwhile, all three sensors based on MoS2/RGO composites exhibited excellent anti-interference performance to ozone with strong oxidation. Furthermore, three sensors based on MoS2/RGO composites were fabricated into a simple sensor array, realizing discriminative detection of three target analytes in 14.5 s at room temperature. This work shows that the synergistic effect between two-dimensional RGO and MoS2 provides new possibilities for the development of high performance sensors.