Abstract: The paper reported a study on the effect of key 3D printing parameters such as filling density, layer height, shell thickness and printing temperature on tensile strength and elongation at break of 3D-printed (PLA) specimens. The tensile strength and elongation at break of the printed specimens were found to increase with the increase of filling density. However, the elongation at break began to drop at a filling density of 100 %, because there was a structural transformation from space grid structure to the entity one for the printed specimens. Moreover, the elongation at break of the printed specimens increased with an increase of layer height, but their tensile strength trend to decrease. On the other hand, their tensile strength and elongation at break increased with an increase in shell thickness and shell thickness. When the print thickness was 1.2 mm, the elongation at break point began to decrease due to the entity structure of cross section in the printed specimens. The printed specimens achieve optimal mechanical properties when being printed in the temperature range of 210～220 ℃.