Assessing machine’s performance through comparing the same or similar machines is important to implement intelligent maintenance for swarm machine.In this paper,an outlier mining based abnormal machine detection algorithm is proposed for this purpose.Firstly,the outlier mining based on clustering is introduced and the definition of cluster-based global outlier factor(CBGOF) is presented.Then the modified swarm intelligence clustering(MSIC) algorithm is suggested and the outlier mining algorithm based on MSIC is proposed.The algorithm can not only cluster machines according to their performance but also detect possible abnormal machines.Finally,a comparison of mobile soccer robots’ performance proves the algorithm is feasible and effective. Assessing machine’s performance through comparing the same or similar machines is important to implement intelligent maintenance for swarm machine. In this paper, an outlier mining based abnormal machine detection algorithm is proposed for this purpose. Firstly, the outlier mining based on clustering is introduced and the definition of cluster-based global outlier factor (CBGOF) is presented.Then the modified swarm intelligence clustering (MSIC) algorithm is suggested and the outlier mining algorithm based on MSIC is proposed. algorithm can not only cluster machines according to their performance but also detect may abnormal machines .Finally, a comparison of mobile soccer robots’ performance proves the algorithm is feasible and effective.