The concentrating method adopts the technological process of pressure reducing circulation flash. The flashing device is a metallic circular cylinder, with smooth internal surface. On the upper part are installed multiple loading ports tangential to the wall of device to increase the area of rubber latex film forming on the wall and make the mositure easy evaporate, the water vapor is exhausted from the top of the flash device. On the bottom of the flash device the atmospheric circulator is installed to achieve the aim of circulation flash. The apparatus used in said method features simple structure, small investment, no harm to the stability of rubber latex, the retention period of rubber latex in flash device being short, rubber coating obviously decreased, rubber latex yield up to 95% odd said method is suitable for concentrating SBR latex of 18-30% solid content.