Electrical transport properties of bismuth vanadate (BiVO4) are studied under high pressures with electrochemical impedance spectroscopy.A pressure-induced ionic-electronic transition is found in BiVO4.Below 3.0 GPa,BiVO4 has ionic conduction behavior.The ionic resistance decreases under high pressures due to the increasing migration rate of O2-ions.Above 3.0 GPa the channels for ion migration are closed.Transport mechanism changes from the ionic to the electronic behavior.First-principles calculations show that bandgap width narrows under high pressures,causing the continuous decrease of electrical resistance of BiVO4.