In the analysis of the typical failure mode, randomness and fuzziness were taken into consideration, time between failures was defined as a random fuzzy variable, then the occurrence chance model was built. Random fuzzy method was used to calculate the occurrence chances of typical failure modes and the ranking. By virtue of the analysis of the occurrence chances and occurrence frequencies, some important conclusions could be made out. The failure mode which influenced the machining center most could be found out, the conclusions provided useful basis on how to eliminate these failure models and how to improve the reliability of machining center of this type.