In order to further improve the reliability of the turbofan engine rotor system assembly, this paper proposes a process failure mode influence analysis method for the rotor system assembly based on the assembly process characteristics of the turbofan engine rotor system. The PFMEA analysis process and PFMEA analysis objects of the rotor system assembly are given, and the PFMEA analysis is carried out with the nut assembly process and the rotor dynamic balance process as examples. The typical process failure modes are given, and the corresponding failure prevention measures are put forward to achieve the purpose of improving the process reliability of the rotor system. In order to improve the efficiency of PFMEA analysis and realize the effective management of the failure mode of the rotor system assembly process, the PFMEA analysis system is proposed, and the functional modules and implementation methods of the system are given.