The single-effect external circulation vacuum concentrator is composed of heater, evaporator, defoamer, condenser, cooler and liquid receiving tank. The parts that contact materials are all made of stainless steel. The equipment is applicable to evaporation and concentration of liquid materials in pharmacy, food, chemical industry and light industry etc. industries. The concentrating time is short and the evaporating speed is high, which can better protect the heat sensitive materials from being damaged.