The POM material is mostly used for components of more mechanical strength, so, it’s very important both in the position of weld-line and polymer strength. Thus, the strength of POM weld-line becomes the main research subject of injection products. This research is exploring the quality and strength of injection products that influenced by POM weld-line. It aims when POM is injecting, based on the conditions of different thickness and different manufacturing process, there comes out finished products with (or without) weld-line, and, we’re going to do tensile test and mechanical characteristic research conforming to ASTM standard. In our study , the model for polymers proposed by Kim and Suh was also modified to establish an empirical correlation for strength with weld-line. This correlation uses the data of tested strength and method of regression analysis to take thickness of test pieces, melt temperature, mold temperature, packing pressure and injection velocity as independent factors. It is expected that this correlation can be used to predict the strength of product with weld-line. POM has similar trend as other plastic material; when the melt temperature, mold temperature and injection speed are accelerating, or, the packing pressure are decreasing, both polymer strength and tensile strength of testing pieces are trending to increase, and, test pieces whose thickness are 1.0 mm having the best tensile strength. Keywords：weld-line；POM；Polyoxymethylene