Hydrogen is a clean and versatile energy source but it is hazardous and highly explosive in air atmosphere due to colorless and tasteless. Despite of these safety disadvantages, hydrogen provides the best route to a sustainable ideal fuel for future. Thus hydrogen sensor has important applications in modern industry, including fuel cell, hydrogen storage and separation, etc. Development of hydrogen sensor with high sensitivity, selectivity and stability has been an important topic in the field of sensor research. Carbon-based nanomaterials have unique physical and chemical properties, high surface area and excellent electronic properties, which are often used as sensitive materials for hydrogen sensor. Nanocarbon based materials show extreme sensitivity towards changes that stems from the susceptibility of their electronic structure to interacting hydrogen molecules. This chemical sensitivity has made them ideal candidates for incorporation into the design of hydrogen sensors. The performance of three nanocarbon based composites (nanocarbon-based materials/metal nanoparticles composite, nanocarbon-based materials/metal oxide composite, nanocarbon-based materials/polymer composite) is analyzed systematically in this paper. Characteristic performance parameters of these sensors, including measuring range, sensitivity, selectivity, response time and lifetime are reviewed and the latest technology developments are reported. In addition, the application prospect and future outlook of hydrogen sensor are addressed. The key issues needed to be solved are also discussed.