Laser transmission welding (LTW) is a new technology for joining plastic components, involves a laser beam passing through a laser-transmitting part being absorbed by a laser-absorbing part at the weld interface. To form a strong bond, it is important that the weld interface be exposed to sufﬁcient heat to melt the polymer without degrading it. This paper investigates the quality of PMMA (Polymethyl Methacrylate) laser transmission welding by using YAG (1.06um) laser. Using the orthogonal experiment method, the specimens under different parameters have been studied. In order to evaluate the mechanical resistance of the welded joint, surface proﬁlometry and metallographic microscopy were employed. It was shown that welding quality was significantly influenced by speed, power, and welding spot size. We summarized the influence of various factors, and eventually obtained the experimental results under different experimental parameters.