Abstract: Assembly process simulation for cable harness in complex electromechanical products is challenging due to the complex structure of the cable harness and its deformation in assembly operations.This paper presents a solution for flexible cable harness assembly process simulation and its key techniques.A digital representation model for complex cable harness is proposed,in which primitive elements are defined and the model is constructed based on the containing relationship and joint relationship between the elements.A hierarchy-chain-based assembly process model which uniformly organizes all the assembly objects,tasks and operations is proposed to represent and store the assembly process,in which assembly tasks and operations may be performed alternatively on rigid part and flexible cable harness.A refined mass-spring model of cable harness with length reservation is built and utilized to calculate the deformation of cable harnesses in typical assembly operations.A prototype system is developed,in which an industrial application is carried out and the proposed solution and key techniques are validated.