In order to study the dynamic evolution law of stress and deformation of deep excavation pit during the whole excavation and support period under the action of double-row micro-pile-anchor-bracing composite support structure in different fill layers, a deep excavation pit project in Qingdao was taken as an example. The slope top displacement, deep horizontal soil displacement, settlement of adjacent buildings, axial force of prestressed anchor cable and steel support were measured and analysed. The results show that the double-row micro-pile-anchor-bracing composite support system can better control the deformation of the foundation pit. The deep horizontal displacement of the soil under each construction node is less than 2.1 mm, and the horizontal displacement of the slope top near the vehicle dynamic load area is larger. During the excavation and support process, the rapid decrease in axial force of the prestressed anchor cable is related to the installation of the steel support. After the excavation and support of the foundation pit is completed, the prestress loss rate of the anchor cable is between 5.1% and 5.6%, and the maximum loss rate of the axial force of the steel support is about 4%. The application of prestressing of steel column can effectively suppress the deformation of adjacent buildings. The research results can provide a reference for the design and construction of deep foundation pit support structure in different fill layers.