For the machining centers which have distinguishing features of small samples and high-reliability, we proposed a Weibull-distribution-based method of Bayesian evaluation to calculate their reliability in this paper. The reliability test platform for machining centers was built and a reliability testing method which was based on the impellers’ machining process was adopted in order to get the field testing samples. Then we selected the machining centers’ reliability of a fixed time as the random variable to determine its prior distribution. The posterior distribution of products’ reliability could be obtained by combining the prior distribution and the field test samples with the application of Bayesian method. Finally, we could calculate the lower confidence limit for the products’ reliability under a given confidence level and the reliability’s mean under typical mission time.