In this work, we use the liquid ammonia method to successfully intercalate potassium atoms into ZrTe5 single crystal, and find a transition from semimetal to semiconductor at low temperature in the intercalated ZrTe5. The resistance anomalous peak is gradually suppressed and finally disappears with increasing potassium concentration. Whilst, the according sign reversal is always observed in the Hall resistance measurement. We tentatively attribute the semimetal-semiconductor transition to the lattice expansion induced by atomic intercalation and thereby a larger energy band gap.Recently, ZrTe5 has attracted increasing attentions because of its mysterious topological nature. DFT calculation predicted that the single-layer ZrTe5 is an ideal two-dimensional topological insulator (2D TI) hosting an indirect band gap of ~0.1 eV [9], but its bulk counterpart resides in proximity of the boundary of topological phase transition from weak to strong TI, through a 3D Dirac semimetal state [9][10][11].Even though great efforts have been devoted to experimentally verify the topological characteristics, the topology of bulk ZrTe5 is still under heavy debate. Either weak TI, strong TI or Dirac semimetal state, has ever been proposed based on the experimental observations with different techniques . The bulk band gap and the topological edge state were detected by ARPES and by STM [14,15,29], which indicates that ZrTe5 is a weak TI. Controversially, signatures of 3D Dirac semimetal were also demonstrated in magnetoresistance [18][19][20]32] and magneto-infrared spectroscopy measurements [12,13,17,24,25]. The strong TI of ZrTe5 has been also proposed [21,27]. In addition, more exotic physical properties have been also found in this material, such as Zeeman splitting [20,33,34], Chiral Magnetic effect (CME) [16], 3D Quantum Hall effect (QHE) [35], Anomalous Hall effect (AHE) [36], Giant Planar Hall Effect (PHE) [37], and Discrete Scale Invariance (DSI) [38,39].Considering the extreme sensitivity of the band structure of ZrTe5 to the lattice constant, the above mentioned experimental divergence may be likely due to the difference in sample growth. It is worthwhile noting that the Dirac node of ZrTe5 is not protected by the crystal symmetry, and a band gap can be opened by a perturbation to turn it into topological insulator. High Pressure was applied to tune ZrTe5 into superconductivity [40], and to induce topological phase transition [41]. The exfoliated ZrTe5 nanosheet shows metallic behavior and tunable resistance maximum, which can be ascribed to the thickness-dependent band structure [42,43]. Up to now, most of the explored ZrTe5 bulk samples, grown by CVT method, behave as metallic