The invention relates to an automatic detection device of cylindrical automobile parts. According to the automatic detection device, a power distribution control box is arranged in a rack, a rotary disk carrier is arranged above the rack, and a bottom outer arc detection device, a middle outer arc detection device and an upper outer arc detection device are arranged on the periphery of the rotarydisk carrier respectively; and each outer arc detection device comprises an outer arc detection seat, wherein an outer arc detection air cylinder and an outer arc detection movable block are arrangedon the outer arc detection seat, an outer arc detection clamp head is arranged on the outer arc detection movable block, an outer arc gauge is installed on the outer arc detection clamp head, the lower portion of the outer arc detection movable block is connected with an outer arc transmission rod, the outer arc transmission rod is matched with one side of an outer arc rotating frame, and the other side of the outer arc rotating frame is matched with an outer arc detection meter. Through the automatic detection device, outer arc changes of the cylindrical parts can be precisely detected through the bottom outer arc detection device, the middle outer arc detection device and the upper outer arc detection device in cooperation with the rotary disk carrier, then an eccentric difference valuecan be precisely determined, and meanwhile the detection efficiency is greatly improved.