This research evaluated a new system of primary treatment for industrial waste water, an"Anaerobic Upflow sludge blanket Reactor" (UASB) was used for the removal of organic matter. The pilot scale system was designed for the wastewater of the Municipal Slaughterhouse in Huancavelica, which was pumped after the pre-treatment (coarse screen and grit removal) to the storage tank of 350 liters for later to perform the treatment of wastewater in UASB reactor scale laboratory. The removal efficiency of organic matter in an UASB reactor was evaluated, for a hydraulic retention time (HRT) of 14 hours with a flow rate of 35mL/min, the minimum efficiency of Chemical Oxygen Demand (COD) removal was 33.66% and maximum efficiency was 76.90% in a temperature range of wastewater from 10 °C to 19 °C. Also for this HRT of 14 hours the amount of total suspended solids decreased from 524.34mg/L to 365.04...