Abstract: Gob-side entry retaining has been widely applied in major coal mining regions across China. As a crucial measure to ensure the stability of surrounding rock in gob-side entry retaining, advance support still require further research in its design. In this study, the N1215 working face of flexible formwork concrete gob-side entry retaining in Ning Tiaota coal mine was taken as the engineering background. We analyzed the evolution patterns of roadway surrounding rock deformation, stress, and support system forces in the retained roadway section without advanced support through field monitoring and numerical simulation. Numerical comparison tests were conducted for different reinforcement anchor cable spacings, hydraulic prop spacings, and advance support ranges. We established 2 quantitative evaluation indexes of surrounding rock deformation control rate and control effect difference rate and proposed a method for designing advance support in flexible formwork concrete gob-side entry retaining. This method was then applied in the N1215 working face of Ning Tiaota Coal mine. Results show that: without advanced support, the depth of the severely broken zone was 3.2 m, and the roof-to-floor convergence was 214.0 mm, the force on the anchor cable was 337.6 kN, and the pressure on the flexible formwork concrete wall was 24.9 MPa, localized compression fracturing occurred in the roadway roof and the flexible formwork concrete wall; with advance support, the stress of the hydraulic prop was 161.6 kN, the roof-to-floor convergence was 48.4 mm, the load of the anchor cable was 217.3 kN, and the pressure of the flexible formwork concrete wall was 20.6 MPa, compared with the non-advance support, the latter 3 indexes were reduced by about 77.4 %, 35.6 % and 17.3 %, respectively. The stability of the surrounding rock of the roadway is effectively controlled by the formwork concrete wall.