Motion and mechanics property analysis is carried out on the five hinged incline arranged and double elbowed force increasing mechanism of injection machine. An optimization design is carried out on the force increasing mechanism by the use of genetic simulated annealing algorithms

and its optional mathematics model is established. And a complete procedure of optimal design is introduced so as to increase the stroke ratio and the amplification of the force

and to decrease the total length of mechanism

which belongs to multi-object optimization problem. The optimal solution of the force increasing mechanism of injection machine is found with genetic algorithms. Compared with the traditional methods

the result shows that the stroke ratio is increased by 8.2%

the amplification of the force is increased by 20.3%

and the total length of mechanism is decreased by 5%.