To evaluate the reliability of NC machine tools,based on AIC and BIC information criteria,a method of model selection and parameter estimation for time-between-failures of multiple NC machine tools with time truncation is proposed.The confidence intervals of model parameters,the reliability given MTBF(mean time between failures) and the warranty time with 90% reliability are all given by Fisher Information Matrix method.At last,Monte Carlo simulation method is used to enlarge sample size of small-sample data to improve the precision of interval estimation.The results show that the interval length of reliability given MTBF and warranty time with 90% reliability are both reduce by 95% and 93% respectively.