It is very important for seeking substitute deposit around exploited deposit to research the method of seeking-deposit prediction. Because of the complexity and fuzzy of the background, genesis and mechanism of mineral formation, it is a difficult point to effectively express the information of these factors. This paper uses fuzzy mathematics function to express relative information for seeking-deposit prediction, establishes fuzzy comprehensive appraisement (FCA) model of predicting deposit in virtue of fuzzy reasoning and fuzzy judgment. The model is proved to be valid through making the choice of prediction factors, the plotting of grid and the practical data test.