Abstract: False positive rate and false negative rate affected the detection creditability of intrusion detection systems (IDS) .A method of multi-IDS cooperation to improve detection creditability was presented after analyzing false negative rate and false positive rate of IDS.The result fusion based on boosting Bayesian classification algorithm, which put different weights on single IDS and sum the result, then choose the greatest one.The experiments show that the method can reduce the false positive rate and false negative rate, then improve the detection creditability.