The invention provides a method for preparing a hydrogen sensitive element based on a quadrature-phase molybdenum oxide nano-belt. The method comprises the following steps: A, a quadrature-phase molybdenum oxide nano-belt powder by a hydrothermal method; B, preparing an interdigital electrode by a photolithographic mask method; and C assembling a hydrogen sensitive element, namely molybdenum oxide powder and an absolute ethyl alcohol mixed liquid, carrying out ultrasonic treatment, dropwise adding the mixed liquid into the center position of the interdigital electrode, and annealing. According to the method, Na2MoO4.2H20 is used as a raw material, the quadrature-phase molybdenum oxide nano-belt with uniform appearance is prepared by adopting the simple hydrothermal method, the using process is simple, the preparation cycle is short, the sample yield is high, and the cost is low; the nano-belt dispersed by ultrasonics is coated to the interdigital electrode to obtain the hydrogen sensitive element with excellent performance; at room temperature, the element has the characteristics of high sensitivity and quick response on low-concentration hydrogen, has excellent repeatability and selectivity on hydrogen, and can meet the requirement of quickly detecting low-concentration hydrogen.