The invention belongs to the technical field of exterior trimming parts, and provides a wave transmission performance testing method and device suitable for an ACC millimeter wave label. The device mainly comprises a control computer, pulse radar, a horn antenna, an action control device, a horizontal angle regulator, an inclination angle regulator, an upper position regulator, a lower position regulator, a front position regulator, a rear position regulator, a left position regulator, a right position regulator, a label fixing jig, an angle reflector and a positioning clamp. On the premise ofgreatly reducing the test instrument installation space and the device cost and in the state of each angle combination of products in the horizontal and the inclined directions, for a traditional testing method, the device is simpler, lower in device cost, wider in test area and more comprehensive, and is closer to the use state of the actual vehicle, can perform large-scale testing for the angleerrors between wave transmitting and receiving while testing the wave transmission attenuation, and is more comprehensive and reliable.