Fault localization techniques are proposed based on the knowledge of software system to improve the reliability of software system. In this paper, based on the decisive factor of failed execution spectrum and the secondary factor of successful execution spectrum, two suspiciousness computation metrics FP3 and FP4 are proposed to compute the suspiciousness of each statement to be the fault. Metric FP3 with different weights for each part is also discussed. On the basis of our proposed

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... ess metrics, a software fault localization algorithm is designed to apply the above proposed metrics to obtain statement ranking to assist effectively locating fault in software. Experiments are conducted on the program with test suites of different types and sizes in the Softwareartifact Infrastructure Repository. The result verifies that our metrics are feasible and effective for fault localization, that our metrics improve the examination rate 12.8% on average over other methods, and that fewer statements need to be examined for fault localization. And the efficiency of locating fault of statement granularity is improved.