The model of maintenance task process is investigated based on colored petri nets(CPN). The method and procdure of maintenance task are developed. The MODAPTS method isused to calculate the work time of each operation step, and the metabolic energy predicting model for human action is used to calculate the energy dissipated of each operation step. The model and simulation of the maintenance, the control of the work sequence and the computation of work load and work time are all presented based on CPN Tools. Takｉｎｇ the nose landing gear tire removal operations of A320 aircraft as an example, the CPN Tools software is used to conduct the modeling and simulation for the maintenance operations to prove the feasibility and effectiveness of the developed model and methods. The ergonomic analysis is introduced into the analysis to evaluate the comfortability of maintenance workers.