The invention relates to a steam drain flash tank, in particular to a soda-water-scouring-resistant steam drain flash tank. The flash tank comprises a flash tank body, a secondary steam exhaust port located in one end of the flash tank body, a drain outlet located in one end of the flash tank body, and a drain pipe assembly located on the inner wall of the middle of the flash tank body. The tail end of the drain pipe assembly penetrates out of the flask tank body, and multiple rows of rectangular small holes are formed in the part, located in a flash tank body section, of the drain pipe assembly. The steam drain flash tank has the advantages of being suitable for the high-temperature and high-pressure working conditions and capable of resisting soda water scouring; and compared with conventional drain flash tanks, the equipment reliability is high, the maintaining cost is low, and the operation safety of the drain flash tank can be ensured.