Abstract: Based on the limit equilibrium method, mechanical models for the overall stability and local stability of a slot wall are established, calculation formulas for the critical slurry volume weight values are derived to guarantee stability of the slot wall during trenching construction, a design method for the slurry volume weight is obtained on basis of slot wall stability during trenching construction of the diaphragm wall and a case application is carried out.The results show that the proposed calculation method for slurry volume weight is reliable and it suggests that slurry volume weight calculations under considering local stability of the slot wall should be taken when the similar project locates in loose strata with sand and pebbles.