The emergence of additive manufacturing technology allowed prototyping the complex 3D shape models. Fused Deposition Modeling (FDM) method in 3D printing is the most widespread material extrusion technology that has great potential to further advance in better quality, low-cost, material, and time optimization. This paper discusses and compares the methods of shape optimization for various models of 3D printed pressure vessels, such as Cylindrical, peanut, pumpkin, and honeycomb, in terms of weight and stress distribution, through FEA simulation in ANSYS software by applying pressure up to 100 MPa inside the vessel. Some optimized shapes of pressure vessels were obtained with uniformly-distributed stress all over the vessel body due to the removal of the less useful parts of the vessel. The most lightweight was the peanut-shaped modified cylindrical pressure vessel, which resulted in a 9.81% weight reduction after applying shape optimization method, and the least average stress undergoing vessel was a simple cylindrical pressure vessel. The simulation results show that the developed technique has a great prospect of possible application in additive manufacturing technology.