To explore the axial compressive stress-strain relationship of Ultra-High Performance Seawater Sea-sand Concrete （UHPSSC） and study the influence of steel fiber volume content on the axial compressive mechanical properties and axial compressive complete stress-strain curve of UHPSSC， the complete stress-strain curve of UHPSSC was obtained through the compression tests with the Instron 1346 universal material ， and the Pycharm curve fitting program was used to fit and modify the existing concrete complete stress-strain curve model. The results show that the higher the steel fiber content， the smaller the damage degree of UHPSSC under axial compression， and the compressive strength and peak strain also increase. The rising section of the UHPSSC stress-strain curve fitted by the existing model is similar to the test curve， and the gap between the falling section and the later stage is large. By modifying the shape parameters of the descending section， a modified model more suitable for describing the complete stress-strain curve of UHPSSC was obtained， and the applicable scope of the modified model was verified.