Abstract: Utilizing data obtained on individual components to obtain confidence limits,it is important to evaluate the reliability of series systems.In this paper,the discussion is based on a special kind of experimental data,satisfying the following condition: 1.The life time of every kind of components in the system has Weibull distribu- tion with different parameters. 2.The experiments are censored by fixed time. A lower confidence limit of the reliability of the series system is given according to the failure numbers of every kind of components in the experiments.Comparison of this method is also made and it is found that this lower confidence limit is the bess in some group of the lower confidence limits.Finally,an example is given.