In order to solve the problem for repairing difficultly of certain type radar’s digital drag equipment, study on the detection and fault diagnosis for the digital drag equipment. It provides the implementation process of detection and fault diagnosis by comprehensively using the communication technology, the software programming technology and the touch screen display technology based on embedded computer technology. Introduce the hardware and software components, and the software working flow chart, and illustrates the detection principles of whole equipment and the circuit board’s by separately taking the digital drag equipment in the direction channel and the SD transform board as the examples respectively. And the fault diagnosis principle based on the fault diagnosis expert database and the help file is also introduced. Summarize the technical problems in applied bus control, hybrid programming, expert experience, and algorithm. The applied results show that the detection instrument has advantages in connection convenience, rapid detection speed and high diagnostic efficiency etc, and it can effectively solve the difficult problems in detection and fault diagnosis for the digital drag equipment.