Abstarct: In this thesis, the design and construction of a carbon monoxide gas sensor baxsed on graphene nanomaterials mixed with tin oxide nanomaterials has been done. Oxidegraphene and oxidegraphene reduced with tin oxide nanoparticles are deposited on the glass sublaxyer in the form of a droplet laxyer. The laxyered samples for making resistive sensors include graphene oxide, graphene oxide with tin oxide nanoparticles, reduced graphene oxide and reduced graphene oxide with tin oxide nanoparticles. The use of a noble mextal such as platinum increases the ability of the sensor to select carbon monoxide gas. The selectivity of the sensor for carbon monoxide gas at a temperature of 25 degrees Celsius has reached 53% with the graphene oxide sensor sample with 10% of tin oxide and with a connection distance of 1 mm. But the same sensor has shown almost no sensitivity to city gas and liquid gas. Field emission scanning electron microscope (FESEM) and Raman analysis were also used to characterize the samples. The working temperature of the sensors is from 25 degrees Celsius to 100 degrees, which has been improved with graphene oxide materials. The sensitivity obtained at room temperature reaches 27% for 30 ppm of carbon monoxide gas and 53% for 1000 ppm. It is worth mentioning that in the combination of these materials and the use of graphene derivatives, the trend of reducing the resistance of the sensor with increasing gas concentration has been improved linearly. Another feature of this sensor is to reduce the starting temperature and remove the heater from the sensor. Decreasing the temperature of the heater and even removing the heater causes the power consumption to decrease. If a heater is used in this sensor, it is required at a lower temperature than similar structures. The maximum operating temperature of the sensor is 100 degrees Celsius.