Abstract: In the forest cultivation expert system, reasoning results are usually made in the face of uncertainty, with knowledge that is incomplete or fuzzy. Uncertainty inference was applied in the forest cultivation expert system to deal with such knowledge. Fuzzy logic was used to express different degrees of certainty or uncertainty of assertions. The certainty factor of specific rules by experts given equalled 1; the weight factor and certainty factor of the uncertainty rule were calculated from the frequency; the certainty factor of rules was calculated using the fuzzy-analytic hierarchy process for the users爷uncertain selection. Furthermore, an inference engine algorithm was designed. The order of questions to be asked was decided dynamically depending upon the answers of the users. On the basis of answers, consulting results along with its confidence factor were provided