The invention provides a brake vacuum assist system, which comprises a main controller (12), a control loop, a vacuum pump (6) and a vacuum tank (7), wherein the main controller (12) is used for controlling the vacuum pump (6) through the control loop; an air intake manifold of an engine (21) is communicated with the vacuum tank (7); the main controller (12) is also used for determining whether the control loop is in an abnormal state or not; and starting the engine (21) when determining the control loop to be in the abnormal state. The invention provides a brake vacuum assist method, which comprises the following steps: the main controller (12) controls the vacuum pump (6) communicated with the vacuum tank (7) through the control loop; the air intake manifold of the engine (21) is communicated with the vacuum tank (7); the main controller (12) determines whether the control loop is in the abnormal state or not; and the engine (21) is started when the control loop is determined to be in the abnormal state. The brake vacuum assist system and the brake vacuum assist method can ensure the effectiveness of brake assistance of a hybrid power automobile.