The three-dimensional (3D) deformation effect of the slope engineering underthe step-by-step excavation for the Antaibao surface mine was analyzed using the FLAG~3Dtechnique. An optimal excavated scheme with a relatively steeper slope angle of 47~(。) instead of 30~(。) was successfully implemented at the west wall in the geological section73200 of the mine area, where the 3D effect of the nonlinear large deformation of theslope was taken into account. Based on the above research conclusion, put forward thecountermeasures of shortening mining length, excavating by different regions, timely footbackfilling to protect the excavated slope, and monitoring and feedback adjustment bystudying the nonlinear effect. The results show that these countermeasures are effective incontrolling maximum deformation and increasing the stability of the slope. The three-dimensional (3D) deformation effect of the slope engineering underthe step-by-step excavation for the Antaibao surface mine was analyzed using the FLAG ~ 3D technique. An optimal excavated scheme with a more steeper slope angle of 47 ~ (.) Instead of 30 ~ (.) was successfully implemented at the west wall in the geological section 73200 of the mine area, where the 3D effect of the nonlinear deformation of the slope was taken into account. Based on the above research conclusion, put forward the countermeasures of shortening mining length, excavating by different regions, timely footbackfilling to protect the excavated slope, and monitoring and feedback adjustment by testing the nonlinear effect. The results show that these countermeasures are effective incontrolling maximum deformation and increasing the stability of the slope.