In view of the lack of the function for cost calculation of foundation pit project in the current Revit software， this paper proposes using the Revit API secondary development technology is to realize the automatic calculation of foundation pit project cost based on the foundation pit project building information modeling （BIM） component family. Firstly， Revit platform is used to establish the BIM model of a foundation pit project and realize the parameterization of the family class of supporting structures of foundation pit projects. Then， with the knowledge of calculation process of foundation pit project cost， the Revit API secondary development technology is used to automatically obtain the parameters of various components in the BIM model of foundation pit project， and to realize the actual quantity calculation， quota application， display and output of data， etc.， based on the calculation formula of foundation pit project cost. Finally， taking a foundation pit project in Changsha city as an example， the automated cost calculation of the actual project is carried out to verify the feasibility of the above Revit-based foundation pit project cost calculation plug-in. The results show that the Revit cost calculation plug-in developed in this paper can achieve automatic cost calculation based on the imported BIM model of foundation pit project， and the results match well with manual calculation. The implementation of this technology makes up for the inadequacy of Revit software in the calculation of foundation pit project cost and foundation pit project cost， improves the efficiency of designers and lays a good foundation for further expanding the application of BIM technology in foundation pit projects.