The analysis of motion and mechanics property is carried out on the five hinged incline arranged and double elbowed force increasing mechanism of injection machine.A complete optimal design procedure is carried out by using improved ant colony algorithms

so as to increase the stroke ratio and the amplification of the force

and to decrease the total length of mechanism.Its optimization mathematics model is established.The procedure of optimal design belongs to multi-object optimization problem.The optimal solution of the force increasing mechanism is found by improved ant colony algorithms.Compared with the traditional methods

the result shows that the total length of mechanism is decreased

the stroke ratio is increased

and the amplification of the force is increased.