In this thesis, forging process of AL6061 in the semi-solid state has been experimentally investigated with solid volume fractions of 0.6, 0.7, 0.8 and 0.9 and various ram speeds 2, 5 and 7 mm/min. The commercial DEFORM-3D finite element software is used to model the forging process of a cylindrical rod. This software is totally used at different deformation methods such as forging, rolling. In these simulations, material model in macroscopic scenario (at high solid volume fraction) is considered as viscoplastic when its liquid volume fraction ignored. The Sellars and Tegart constitutive model is used to determine material behavior in this software. It is assumed that workpiece is able to deform plastically but molds are rigid. In addition to, friction coefficient between specimen and dies is fixed and based on Coulomb’s model. In the thesis, the linear relationship between temperature and solid volume fraction is considered and that is the case in this study. Because of the axisymmetry geometry of experiment, only one-fourth of the specimen is simulated. For the experimental tests, STM-150 compressing and pulling machine is used. In order to run simple compression test, 6061 Al alloy samples with 10 mm in diameter and 18 mm in height are prepared using turning machine. The sample preparation was based on ASTM-STP 608 standard. The samples have been put into machine furnace and heated for 10 min to reach target temperature. There are several thermocouples inside the furnace to control the temperature gradient inside the chamber and a thermocouple to measure specimen temperature. The upper mold compressed the specimen for 10mm. To compare simulation and experimental results, force-stroke curves are obtained in both processes and the whole solid volume fractions and various ram speeds that are maintained. The results show that there are good agreements between simulation and experimental curves at ram speeds of 2, 5 and 7mm/min and solid volume fractions of 0.6, 0.7, 0.8 and 0.9. They also show that the deformation trend in semi-solid state is totally depends upon strain rate. It can't be used higher ram speeds in experimental process, because the material doesn't have enough time to deform and it collapses. Furthermore, the semi-solid forging is compared with solid and hot forging simulation. By analyzing of results it can be claimed that deformation trend in semi-solid state is totally different with solid and hot forming process. In the next section, a specimen with difficult shape is simulated in semi-solid state and compared with solid forging. This comparison shows that forging in semi-solid state is more useful for complicated forming. Keywords Semi-solid state, AL6061 alloy, force-stroke curves, viscoplastic, forging ?