Aiming at the conflict and uncertainty of the test data required in the quality assessment, and the incompleteness and inaccuracy of the condition assessment, an improved method of evidential reasoning (ER) is proposed. After the quality grading and test data pretreatment, the conflict between the information and the overall uncertainty are assigned to each level of probability to reduce conflict and overall uncertainty between the evidence assessed. The method is applied to the missile equipment quality condition assessment, and the results and algorithm comparison show that the improved evidence reasoning method can effectively reduce the conflict of evidence, and the overall uncertainty of condition assessment is greatly reduced. The principle of the method is simple, the theoretical basis is sufficient, and the program is convenient to be realized.