Abstract: On the basis of two main common cause failure mechanisms, common cause failure rates and α factor of target system with lacking data were analyzed, expressions of their mapping up and down were deduced, and then mapping ratio θ was introduced to revise their expressions. Moments of common cause failure rates were obtained in the terms of the weights by using probability generating functions, and expressions of the moments of each order common cause failure rate were obtained by combining mapping method. The results show that using mapping method and probability generating function to analyze uncertainty of common cause failure parameters is an effective method to combine experience data of source systems to estimate common cause failure parameters.