The invention discloses a circuitry built-in test device based on a boundary scanning mechanism, which includes a subsystem-level BITE, a circuit board-level BITE and a component-level BITE, wherein the subsystem-level BITE is mutually connected with an external data management system through a system-level high-speed data bus, and is mutually connected with the circuit board-level BITE and other to-be-tested circuit boards in other subsystems through a system test and maintenance bus in the lower level; and the circuit board-level BITE is mutually connected with the component-level BITE and other components in the circuit board through a boundary scanning test bus. The device can realize different-level fault layered diagnosis and positioning of the complicated circuitries of aero spacecrafts as satellites, and provides reference for design of the circuitry built-in test devices of other aerospace products.