<FONT face=Verdana>Reliability of Traveling Wave Tubes (TWTs) are crucial for operation of many armaments. However

due to the complexity and expensiveness of TWTs

the way to precisely evaluate their reliability under small sample size is still the problem to face. In this way

prior information

such as expert experience and historical data

can be used to enhance the estimation precisions. With a fuzzy prior distribution construction method for TWTs introduced

based on fuzzy membership functions

prior information can be effectively merged with test data using Bayes method. Reliability evaluation for some satellite TWTs shows that

the precision can be enhanced notably for data with small samples or high truncation levels by using Bayes estimation with normal fuzzy prior distributions. And the estimation can be modified by increasing test information. Furthermore

the bandwidth of the normal priors can be used to adjust the proportion of prior information within the post-Bayes distributions.