There are lots of slugs produced in weaving process, which seriously affects the quality of silk products. In this study, red pulse laser was used as the signal source. Light signal goes through the shed, then enter the ARM (Advanced RISC Machines) embedded computer systems for analysis. Thus the slug situation of shed state is judged and the loom is controlled to make corresponding adjustments to prevent more slug formation. Plenty of tests are carried out on various slugs and satisfied results are gained. It shows that using ARM to develop the Loom Slug Detection Apparatus is feasible.