The invention provides a detection device and detection method for an oil producing wellhead abraded by an oil tube rod. A box body is divided into a separation chamber and a detection chamber through a baffle, wherein the separation chamber and the detection chamber are mutually independent. A detection rod stretches into the detection chamber to detect the total iron ion concentration. The detection rod makes full contact with watered oil, so that a chemical reaction is generated between sulfate matter in the detection rod and iron ions, the color changes, and the total iron ion content in produced liquid increases gradually along with the abrasion degree of downhole tubing and a pumping rod. The detection rod contains matter which is highly sensitive to the iron ions, and the color change is quite obvious. When the total iron ion content reaches a certain quantity and changes suddenly, an abnormal condition is showed by the color of the detection rod. The detection rod can be taken out to be compared with a reaction spectrum, the abrasion condition of the downhole tubing can be early warned, and a worker is prompted to consider of arranging pump previewing operation. Test results provide guidance for production and management of an oil well, and the loss caused by high-frequency operation of rod leakage, oil tube leakage and liquid blockage of the oil well can be avoided.