3D printing has been recognized as an efficient and sustainable technology in the fields of advanced manufacturing. In the past few years, a considerable research, including basic theoretical research, technology innovation and industries application, have been conducted to promote 3D printing for a better performance in manufacturing. However, the benefits of 3D printing from environmental perspective are still to be seen and its sustainability is also a mystery. This paper presents a critical review about the qualitative and quantitative environmental impact of 3D printing to provide a comprehensive understanding of 3D printing for the public and provide a better guide for the future research. In addition, based on the principle of multi-objective optimization, this paper proposes a novel framework for 3D printing processes sustainability assessment and improvement by integrating the product Computer Aided Design (CAD) and Life Cycle Assessment (LCA). At last, recommendations about major concerns when analyzing the sustainability of 3D printing are put forward, which might be considered for the coming research.