Abstract: In process of the arranging experiment data for determining the damage threshold, it is found in some samples that the distribution of the data points of the experiment results deviates obviously from the linear distribution. Under this situation, as the damage threshold is determined from the linear extrapolation of the measured energydensity dependent damage probability based on the ISO11254, another damage threshold of zero probability is obtained by the different nonlinear fit of the experiment data. After making a comparison between these two values and contrasting them with the experiment results, it is obtained from some samples that the damage threshold of zero probability extrapolated by the nonlinear fit is more close to the “real” damage threshold.