The purpose of this paper is to compare the forging effects according th the shape of preforms of cup shaped powder forging product, and extend the application of powder forging technology to more complicated cup-shaped products like pistons. In order to this, preforms are provided by compacting, sintering, and machining in various shapes, then forged to final shape of products. The workability for sintered aluminium powder material is examined. Density and strain loci of forged products are compared, and the most effective shape of preform is proposed. The preform for a piston of 50mm in diameter is provided and hot forged to final product.