In this work, the performance of up-flow anaerobic staged reactor (UASR) was investigated for biogas production from polyester wastewater which are contaminated with heavy metals and 1,4-dioxane. three different values of average organic loading rates (OLRs) were applied 0.31±0.037, 0.71±.082, and 1.069±0.27 g COD /1.d respectively at constant hydraulic retention time (HRT) of 96 hrs, in order to study their effects on biogas production, removal efficiency of 1,4-dioxane and COD. The results indicated that the biogas production obtained at three applied OLR were 14.7 ± 0.17 l/ d., at OLR 1.069±0.27 g COD /1.d., 7.5 ± 0.2 l/ d., at OLR 0.71±.082 g COD /1.d., and of 5.5 ± 0.11 l/d at low OLR, 0.31±0.037 g COD /1.d respectively. Biogas is produced by the metabolism of acetic acid, lactic acid, and a small amount of propionic acid. Moreover, CODt and CODs removals efficiency were 79% and 80% at OLR 0.71±.082 g COD/l.d. The highest removal efficiencies were recorded at OLR 0.71 g COD/l.d. Effect of C/N ratio and heavy metals on biogas production were highlighted. Additionally, different HRTs were studied, to carefully describe the performance of UASR.