The invention relates to an automatic detection device of a cylindrical automobile part. A rack is internally provided with a distribution control box, the upper portion of the rack is provided with a rotary table carrier, the periphery of the rotary table carrier is provided with a bottom outer arc detection device, a middle outer arc detection device and an upper outer arc detection device separately, the bottom outer arc detection device, the middle outer arc detection device and the upper outer arc detection device are each provided with an outer arc detection base, the outer arc detection base is provided with an outer arc detection air cylinder and an outer arc detection mobile block, the outer arc detection mobile block is provided with an outer arc detection clamp head, an outer arc detection device is installed on the outer arc detection clamp head, the lower portion of an outer arc detection mobile base is connected to an outer arc transmission bar, the outer arc transmission bar is coordinated with one side of an outer arc rotational stand, and the other side of the outer arc rotational stand is coordinated with an outer arc detection meter. In the automatic detection device of the cylindrical automobile part, through coordination of the bottom outer arc detection device, the middle outer arc detection device and the upper outer arc detection device and the rotary table carrier, the outer arc change of the cylindrical automobile part can be precisely detected, accordingly an eccentric error value can be accurately determined, and meanwhile the detection efficiency is greatly improved.