Abstarct: Two-dimensional transition mextal dichalcogenides (2D TMDs) are a family of materials consisting of over 40 compounds with the generalized formula of MX2. In the bulk form, MX2 compounds are laxyered materials (van der Waals solids) in which there is strong intralaxyer bonding and weak interlaxyer bonding. After the synthesis of graphene, in the first year of this century, a wide research field on two-dimensional materials opens. In this thesis, graphene oxide, thermally reduced graphene oxide, chemically reduced graphene oxide, and molybdenum sulfide/reduced graphene oxide Nano-composites were synthesized and characterized. Their gas sensing properties were disused. The structural properties, elemental composition, surface morphology of the synthesized samples were studied by XRD, FT-IR, RAMAN, EDAX, FE-SEM and UV-vis analysis methods, respectively. In this research, Grapheme oxide (GO) was produced via modified Hammer method using graphite powder and potassium permanganate (KMno4). Graphene oxide results from the breakdown of weak van der walls bonds between two-dimensional graphite laxyers. In this process, functional groups are formed between the plates. In order to reduce the graphene oxide Chemical reduction and thermal reduction at 300, 900 °C was used. Then thermal reduction sample was improved via microwave method. Also Molybdenum sulfide/reduced graphene oxide composite was prepared by hydrothermal method. In Raman analysis, changes in the intensity ratio of the twin RGO peaks relative to the GO indicate a successful and excellent reduction using this method. The results of the infrared spectrometry show a decrease in the intensity of the peaks of the oxygenated groups and the oxidation process. The microscopic images of the samples also show the two-dimensional structure of the RGO crumpled sheets and molybdenum disulfide Nano-flower. Graphene oxide is an insulating material that exhibit excellent conductivity after reduction process. The synthesized composite sensor showed better sensitivity compare with the reduced graphene oxide sensor at room temperature and 100 ° C.