The invention relates to a preparation method of one-dimensional metal molybdenum oxide nanobelt/graphene composite semiconductor material. According to the preparation method, graphene oxide and Na2MoO4.2H2O are used as raw material, and the molybdenum oxide nanobelt/graphene composite material is prepared through a one-step hydrothermal method. According to the preparation method, the technology is simple, the controllability is high, the preparation period is short, the yield is high, the cost is low, and the defects of poor repeatability and unsteady performance in traditional preparation of molybdenum oxide nanobelt/graphene composite material can be overcome. Moreover, according to the invention, the ultrasonically dispersed molybdenum oxide nanobelt/graphene composite material is spread on an interdigital electrode through a simple method, sequentially, a hydrogen-sensitive element with excellent performance is prepared, the response time of the hydrogen-sensitive element to low-concentration hydrogen of 1000ppm (0.1%, volume fraction) hydrogen at room temperature is only 10.6s, and the sensitivity of the hydrogen-sensitive element to low-concentration hydrogen of 1000ppm (0.1%, volume fraction) hydrogen at room temperature is about 95%, so that the hydrogen-sensitive element has the advantages of high sensitivity, quick response and short reply time.