To solve the multi-line layout problems of equipment with unequal area and fixed shape, a free-for-line layout strategy was proposed and the definition of net line space was presented. An optimization mathematic model was built with the objectives of the reversed logistics and net line space. Based on introducing the immune system population diversity as sign of population evolution, an improved adaptive genetic algorithm (IAGA) was put forward. The nonlinear adaptive adjustment function was achieved for crossover and mutation probability. Finally, the proposed algorithm was compared and evaluated. The results indicate that the algorithm can quickly obtain the nearly optimal solution. It is very useful for solving the combinatorial optimization problems of the multiline layout problem of equipment.