Abstract: The Paper presents a new algorithm for minimizing cut sets of fault trees of agricultural machinery diagnosis by microcomputer directly. In this algorithm,the data base technique is used. The structure of fault tree is transformed into the structure of date base, applying the data processing technique, the non-linear calculation is replaced by linear one, thus the computer' s internal storage is saved and the calculation speed is increased. The design and program implementation of the algorithm are clear. It can be mastered and operated easily.