It is evidence that modified condition/decision coverage (MC/DC) is an effective verification method and can help to detect safety faults despite of its expensive cost. In regression testing, it is quite costly to rerun all of test cases in test suite because new test cases are added to test suite as the software evolves. Therefore, it is necessary to reduce the test suite to improve test efficiency and save test cost. Many existing test-suite reduction techniques are not effective to reduce MC/DC test suite. This paper proposes a new test-suite reduction technique for MC/DC: a bi-objective model that considers both the coverage degree of test case for test requirements and the capability of test cases to reveal error. Our experiment results show that the technique both reduces the size of test suite and better ensures the effectiveness of test suite to reveal error.