If TFT array substrate has large via hole resistance and poor current withstanding properties, via hole is easy to burn up which will cause abnormal display. At present, the influencing factors and mechanism of the via hole resistance and current withstanding properties are not clear, which restricts the preparation and application of the via hole with good current withstanding properties. In this paper, the experimental results show that reducing block resistance of indium tin oxide film (ITO), reducing the slope angle of via hole and increasing contact area between ITO film and metal can reduce via hole resistance and improve current withstanding properties of the via hole. Combined with the analysis of via hole structure and mechanism, it is pointed out that the via hole resistance is mainly composed of ITO film resistance (RITO) and the via hole contact resistance (Rcontact). Either reducing block resistance of ITO film or the slope angle of via hole will reduce ITO film resistance (RITO), while increasing contact area between ITO film and metal will reduce the via hole contact resistance (Rcontact). The via hole current withstanding properties is worse in middle of the substrate because the ITO film block resistance and via hole slope angle are larger. Thicken ITO film, regulating insulating layer film quality and dry etching parameters to reduce slope angle and increase via hole contact area are effective ways the via hole resistance and improve the via hole current withstanding properties under the premise of meeting product optical quality standard.