In this paper, algorithms are presented in order to determine the best disassembly sequence for a sub-assembly and a system life-cycle model for disassembly-assembly line design. The main contribution consists in the determination of a sequence which has the minimal number of components to disassemble, taken into account several criteria: stability, the geometrical form, operations done in parallel, and the irreversible operations. The integration of assembly and disassembly is advantageous for the activation of higher value as per assembly, repair, maintenance and reuse of parts, components and products.