In view of existing features of activated sludge process without primary sedimentation tank and the requirements on grit removing sedimentation tank,in this paper,two types of grit clarifier-horizontal and whirling one are suggested with consideration of grit removal efficiency for fine particle size during its design.Then,according to the sedimentation theory,the principle of grit removal,control of key technical parameters and type choice of grit discharge equipment are analyzed.It can serve as reference for the design of grit clarifier.