Abstract: With TC4 titanium alloy powder as raw materials, four types of specimens with different shapes and sizes, including the columnar specimen with diameter of 16 mm, the fatigue specimen with diameter of 7 mm in parallel section and diameter of 16 mm in clamping section, the plate specimens with thickness of 10 mm and 22 mm were directly formed by selective laser melting (SLM) . The z-directional (forming direction) residual stress of the specimen was measured by the contour method. The effects of specimen shape and size on residual stress were analyzed. The results show that the internal residual stresses of SLM formed specimens were compressive stresses, and the surface residual stresses were tensile stresses. The distribution shape of residual compressive stresses was similar to the shape of the specimen cutting section, it was nearly circular and nearly rectangular, respectively. Compared with the 22 mm-thick plate specimen, the distribution span and amplitude of the internal compressive stress on the centerline in the thickness direction of the 10 mm-thick plate were lower, the distribution span of the internal compressive stress on the centerline in the width direction was unchanged, and the peak value of the compressive stress was reduced by nearly 1/2. The internal compressive stress distribution and amplitude of SLM formed specimen were greatly affected by the shape and size of the specimen, which was attributed to the different constraints in forming of specimens with different shapes and sizes.