The invention discloses a hardness-variable protective nucleic acid detector and a use method thereof, and belongs to the field of nucleic acid detection. In the process of wiping the throat of a human body to extract secretions, when the human body makes some vomiting actions due to nausea and sensitivity, the oral cavity excessively contacts with and squeezes a double-state sampling rod, an air bag head is subjected to buffer deformation, and thus, on one hand, primary protection on the oral cavity and throat is achieved, on the other hand, along with compression deformation of the air bag head, a rubber sealing ball and a sliding ball gradually move, air in an inflation pipe sleeve and the air bag head is finally released, the inflation pipe sleeve and the air bag head can be shrunk under compression, and the whole double-state sampling rod cannot maintain a linear state due to loss of air support, loses hardness and support force, so that the double-state sampling rod is in a free and soft state, is unlikely to squeeze the oral cavity, and secondary protection for the oral cavity is realized. The detector is of a detachable structure, part of the structure of the detector can be recycled, so that the production cost is reduced.