A method and apparatus for improving yield ratio of testing are disclosed. The method includes the following steps. First of all, devices are tested and electromagnetic interference is measured. Next, the test results are examined for whether the devices pass the test or not. Then, electromagnetic interference data are examined for whether the electromagnetic interference data are over a predetermined standard if the devices fail the test. The above-mentioned steps are performed again if the electromagnetic interference data are over a predetermined standard. The test is terminated if the devices still fail the test and the values of electromagnetic interference are still over a predetermined standard.