The student early warning is a type of the problem that involves intelligence factor and non-intelligence factor and indetermination factor, the challenge lies in ascertaining early-warning factor. In this paper, basing on analyzing association rule and the principle of Apriori algorithm, a new Apriori algorithm has been designed for solving complexity of predictors in an early warning system of college students. At first, make sure the count K of item gathering the largest frequent itemset. Then directly make the largest frequent itemset LK by the items, whose count of item is larger than K or equal to K. We can acquire the k-1、k-2 frequent itemset with the same method. We carry on an experiment on the new algorithm. As a result, the efficiency of the new Algorithm is raised obviously. And along with data quantity aggrandizement, the time consumed changes inconspicuously. That is to say the algorithm keeps very high efficiency.