A turning thread automatic diagnosing method includes collecting a spindle actual speed and a feeding shaft actual speed of a lathe; based upon the spindle actual speed and the feeding shaft actual speed, continuously calculating thread errors to obtain a thread error curve; and analyzing an error cause according to the thread error curve. In addition, a turning thread automatic diagnosing system is disclosed, using the method. A data processing system and a storage medium are also disclosed. The technology of the embodiments can automatically identify the problem causing a thread error and provide a corresponding solution.