With the rapid development of intelligent driving, in order to better protect the safety of occupants, a seatbelt assembly with a motor-driven mechanism has been developed, which can provide protection under the following working conditions: 1.When the FCW detects an impending collision and the vehicle performs an emergency brake, the MSB actively pre-tensions at high speed in advance to restrain the occupant's sitting posture; 2.When the FCW detects a potential vehicle collision and alerts the vehicle to perform an emergency brake, the MSB performs an emergency pre-tension to restrain the occupant's forward movement; 3.When the vehicle is cornering at high speed, generating large lateral inertia, the MSB actively tightens to maintain and restrain the occupant's sitting posture; 4.When the LDW detects that the vehicle is deviating from its lane and there is a risk of collision, the MSB retracts and releases the webbing to shake, reminding the driver to adjust driving; 5.After the occupant is seated and finishes wearing the seatbelt, the MSB actively eliminates slack in the belt to adjust the occupant's seatbelt wearing state; 6.When the occupant unbuckles the seatbelt (with the buckle and tongue separated), the MSB automatically retracts the webbing at a constant speed to return the tongue and webbing to the B-pillar.