Abstract: The non-parametric method is conventionally used to evaluate data in lot acceptance testing (LAT) of transient ionizing radiation. But the evaluation results are very conservative and will lead to an increase of the trial cost. The ordering method in the sample space was introduced and applied to compute the lower confidence limit of survival probability based on zero-failure data and was compared with the non-parametric method both theoretically and via a practical LAT on QG-Ⅰ. It is concluded that the ordering method can not only improve the lower confidence limit of survival probability but also expand the scope of dose rate corresponding to the lower confidence limit. Results indicate that the ordering method improves data utilization and makes the evaluation less conservative and can save the trial cost.