The invention discloses a two-stage anaerobic treatment system for cassava alcohol wastewater. The system comprises a primary heat exchanger, a high temperature anaerobic fermentation tank, a primary drum screen, a secondary drum screen, a secondary heat exchanger, a sedimentation pool, an air floatation pool, an adjustment pool and a medium temperature UASB reactor. Wastewater goes by the primary heat exchanger for cooling, enters the high temperature anaerobic fermentation tank for high temperature anaerobic fermentation, goes by the two-stage drum screen, the secondary heat exchanger, the sedimentation pool and the air floatation pool for removing suspending matters and partial COD, and enters the UASB reactor for medium temperature anaerobic fermentation. The system has the following advantages: biogas generated in the two-stage fermentation is collected and used, and wastewater enters a subsequent aerobic segment for continuous treatment; and the whole treatment process flow is concise, the management is convenient, the energy consumption of the production and the operation is low, the treatment efficiency is high, and sludge has a less output and is easy to dispose.