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The ZrTe5 is known as a high mobility thermoelectric material. In 2014, Weng et al. predicted theoretically that the monolayer ZrTe5 is also a 2D topological insulator. In early works, scientists were focused on the abnormal metal-insulator transition as the temperature decreases. However, the physics nature of this phenomenon is still under debate. Here we have explained this by temperature-induced swapping of the dominating carriers from holes to electrons, evidenced by magneto-transport and angle-resolved photoemission spectroscopy (ARPES) measurements on single crystal ZrTe5 samples. Both methods indicate that the Fermi level of ZrTe5 raises from the top of the valance band across the conduction band as the temperature decreases. This is also accompanied by changes of the lattice constants. Our first principle calculation suggests that the shift of the Fermi level comes from the band structure change caused by the temperature variation.