We propose a novel approach to locate errors in complex counterexample of safety property. Our approach measures the distance between two state transition traces with difference of their control flow. With respect to this distance metrics, our approach search for a witness as near as possible to the counterexample. Then we can obtain the set of control flow predicates with difference assignment in witness and counterexample. Run this witness-searching algorithm iteratively, we can then obtain a predicate list with priority. A predicate with higher priority means that this predicate is more likely the actual error. Experiment result shows that our approach is highly accurate.1