In order to study the influencing factors and sensitivity of local stability of the diaphragm wall in sandy soil layers, the disturbed area of trenching construction was determined through the Rankine active earth pressure theory. The local instability model of trench wall was constructed as a semi-elliptical oblique section. The solution of local stability coefficient of diaphragm trench wall was derived by using the limit equilibrium analysis method. The sensitivity of weak interlayer parameters, mud parameters, groundwater level depth, ground load, trench section length and other factors to the stability of trench wall was analyzed. The results show that the increase of the internal friction angle and cohesion of the weak interlayer increases the stability coefficient of the trench wall by 288% and 83%, respectively, the increase of the mud weight and liquid level depth increases the stability of the trench wall by 69% and -24%, respectively, and the increase of the groundwater level, ground load and trench section length increases the stability of the trench wall by 53%, -6% and -13%, respectively. The analytical solution proposed in this study can provide a theoretical basis for the stability evaluation of diaphragm wall crossing weak interlayers in sand soil layers. By optimizing mud parameters and construction technology, the trench face stability of diaphragm wall can be effectively improved, which has important guiding value for the design and construction of diaphragm wall projects in water-rich sand soil layers.