A vehicle-mounted security inspection system includes a mobile chassis. A first cabin provided on the mobile chassis includes an object security inspection apparatus, which is used to perform a security inspection on an object. A second cabin provided on the mobile chassis includes a human body security inspection apparatus which is used to perform a security inspection on a human body. The second cabin is flexibly connected to the first cabin, so that in a first state, the second cabin is located at one end of the first cabin in a longitudinal direction of the mobile chassis, and in a second state, the second cabin is located on one side of the first cabin in the longitudinal direction of the mobile chassis.