A 10 W diode pumped solid state (DPSS) laser is employed for through-transmission welding of polycarbonate to study the properties of weld joint. Optical microscope (OM), scanning electron microscope (SEM) and tensile machine are employed for analyzing the morphology of the welded joint, fracture and tensile-shear stress. The results show that under the condition of 8 W laser power, 50 kHz laser frequency, 350 mm/s scanning velocity and 0.1 mm scanning interval, the tensile-shear stresses of the samples are 44 MPa, which research 68% of the basic materials. Layering and pores in the welded joint are the main factors of low mechanical properties and different fracture mechanisms and with this approach we can get weld joint with good mechanical properties.