An adjustable supporting bar is mainly used for supporting a high-voltage test wire. The adjustable supporting bar comprises a base, a bar body, and a wire clamp assembly. The base can be adsorbed on an object prepared from steel through magnetic force. The bar body is a telescopic insulating bar, and one end of the bar body is connected with the base through a rotating mechanism and can rotate relative to the base. The wire clamp assembly is arranged at the other end of the bar body, and can rotate relative to the bar body. The adjustable supporting bar provided by the invention is applicable to different working environments, can keep a high-voltage test wire an enough safety distance from the metal shells of test equipment and surrounding equipment, and improves the safety of high-voltage test and the working efficiency.