Using 3D simulation software DEFORM-3D, the semi-solid forming process of 7075 aluminum alloy deep cavity cylinder was simulated,the effects of billet temperature, die temperature and loading speed on the forming process of cylinder were analyzed.The results show that,increasing the die temperature and billet temperature can significantly reduce the deformation resistance of billet during cylinder forming;increasing the mold temperature and loading speed can reduce the heat loss and improve the filling capacity of semi-solid billet.The optimal process parameters are as follows: billet temperature 610℃, die temperature 350 ~ 400℃, punch loading speed 15mm/s,at this time, the maximum equivalent stress value of the material is 69.9MPa.Tests have shown that,semi-solid forming is carried out under optimized process parameters. The shape of the cylinder is complete, the surface quality is high, the structure is compact and there is no forming defect.