Laser transmission welding is widely used in medical, electronics, automobile and package fields due to its excellent welding performance. At present, fiberglass-doped is an important method of modified plastic for improving the usability of plastic products. However, fiberglass-doped method can contribute to a sharp decline in plastic laser transmittance, and it presents a technology difficulty for laser transmission welding. To solve this problem, a technology study of laser transmission welding of fiberglass-doped ABS and PP is carried out in order to obtain the best welding process. Firstly, according to the mechanism of laser transmission welding, the process problems of welding fiberglass-doped ABS and PP are pointed out. Secondly, the preliminary welding experiment of fiberglass-doped ABS and PP is implemented to obtain the suitable scope of welding process parameters. Then, the Taguchi experiment is accomplished to analyze the effects of process parameters on shear strength through proposing the concept of laser energy per unit of area. The experiment analysis shows that the laser energy per unit of area can well describe the relationship between weld shear strength and process parameters. Besides, the optimal laser energy per unit of area for welding fiberglass-doped ABS and PP is 0.43 J/mm2.