Abstract: Washing process (purification of metatitanic acid) is a very important process in the process of titanium pigment production by sulfuric acid method.Separation effect of steam-water in washing process will directly affect washing time and effect.In many titanium pigment enterprises,there are many problems,such as oversize and excessive number of separation tanks,serious vacuum loss as well as bad steam-water separation effect due to unreasonable design of traditional steam-water separation system and tanks,which restrict washing effect badly.In allusion to these problems,a method and a thread that steam and water to be separated in the mixing pipes have been put forward based on the process route,equipment,optimal allocation of each unit,and installation requirements.Through the improvement,separating efficiency was increased,vacuum loss was reduced and washing time was shortened.