Abstract: Using the hierarchical exponent test data,an information theory method for calculating approximate confidence limit of system reliability was presented.The equivalent system exponent data were obtained from the hierarchical test data based on the principle of equal information quantity.The approximate confidence limits of the system reliability were given from the equivalent system exponent data according to the principle of unit reliability assessment.The application of the method was described by way of examples.The results are very close to those of the traditional Classical and Bayes methods and show that the method is correct and valid.