The objective of the research is to study the ability of baker's yeast wastewater (BYW) treatment by a Up Flow - Anaerobic Sludge Blanket (UASB) reactor. The effect of the temperature of BYW on the efficiency of treatment in a UASB was investigated and the experiments showed that it is possible to achieve good removal efficiency of chemical oxygen demand (COD) (10200-16320) mg L-1 when the temperature of BYW is about (35±2)°C and hydraulic retention time (HRT) = 24 h. The removal efficiency fit with temperature value of wastewater in UASB reactor for the following values of temperature of (11±2; 16±2; 26±2; 26±2; 31±2; 35±2) °C. The removal efficiencies of COD were: (36.6%; 37.9%; 43%; 44.2%; and 48.8%) respectively. The effect of changing the values of HRT on the efficiency removal at a temperature (35±2) °C value was investigated. The experiments illustrated that it is possible to achieve good removal efficiency for high concentrations of COD when the temperature of the BYW is fixed at (35±2) °C and HRT>=24 h. The removal efficiency fits with HRTs values. For the following values of HRTs: (18; 24; 30; 36) h, the removal efficiencies of COD were: (32.9%; 48.8%; 48.95%; 51.3%) respectively.