The invention provides an emergency power supply and an emergency system, and the power supply comprises a controller and a power supply unit. The controller is connected with the power supply unit. The controller and the power supply unit are respectively connected with target equipment. The controller is used for detecting whether an external power supply which supplies power to the target equipment stops the supply of power to the target equipment or not in real time. When the external power supply is detected to stop the supply of power to the target equipment, a power supply signal is transmitted to the power supply unit. The power supply unit is used for supplying power to the target equipment when the power supply signal transmitted by the controller is received. The power supply and system, which are provided by the invention, can improve the safety of the equipment.