Aiming at problem of low efficiency caused by relying on manual maintenance only while repairing suppress sighting device

a fault diagnosis expert system is proposed. The improved discernibility matrix（ IDM）attribute reduction algorithm based on rough set theory and fault tree is used to achieve knowledge acquisition of expert system

the improved forward reasoning algorithm is put forward to design reasoning machine of expert system. The results show that this fault diagnosis expert system can make the right judgments on the fault very quickly

it can also give the reason and advice to the failures

and thus proves reliability of the design of fault diagnosis expert system.