The invention relates to the field of car assembly, in particular to an automatic assembly method for a car interior trimming door plate. The method comprises five sections of independent working position areas which comprise a door plate assembly clamping area, an ultrasonic welding area, an automatic bolt installing area, an automatic clamping and buckling installing area and a material taking area. All of the working position areas can be used according to a step sequence, dismounted from a flow line, and used as an independent working unit. Automated operation is achieved under the control of a controller procedure through equipment parts such as a servo module group, a mechanical hand, an ultrasonic welding machine, an automatic screw machine, an air cylinder and a motor. According to the automatic assembly method, the purposes are to save the labor cost, improve the productivity, and improve the production efficiency.