With the same process parameters and the heat treatment/hot isostatic pressure technique, two batches of Hastelloy-X alloy specimens with different powder compositions are processed by selective laser melting, in which batch A is high in carbon and manganese contents and while batch B is high in silicon content. The tensile properties at room and high temperatures are tested. The microstructural characteristics and tensile fractures at room temperature are investigated. The results show that the transverse structural morphologies of forming parts from two kinds of materials are similar, but the grain morphologies and the intragranular carbides are quite different in the longitudinal structures. The microstructures of batch A materials are equiaxed grains and the intragranular carbides precipitate more, and while the microstructures of batch B materials are columnar crystals along the longitudinal direction. The tensile properties of batch A specimens at room and high temperatures reach the standard of bar forgings, and while those of batch B specimens exhibit much a more obvious anisotropy in the transverse and longitudinal directions. The longitudinal tensile properties of batch B materials are characterized by low strength and high plasticity, and are subject to the effects of carbon and silicon elements. There exist an obvious plastic deformation for the fractures of the two batches of materials at room temperature, which are cup-like intergranular dimple.