In order to solve the problem of difficult support of the large section soft rock open-off cut in No.1208 Face of Fusheng Mine, the geological occurrence conditions of the roadway were comprehensively analyzed. The stability characteristics of the surrounding rock of No.1208 Face were systematically studied by using geomechanical analysis and numerical simulation methods, and a reasonable support design scheme and support parameters were proposed. The simulation results showed that the stability of the surrounding rock of No.1208 working face open-off cut was between unstable and extremely unstable. Under unsupported conditions, the maximum subsidence of the roof was 725mm, the maximum floor heave was 156mm, and the two sides moved closer by 322mm. After optimizing the support conditions, the stress conditions of the surrounding rock were improved. The maximum subsidence of the roof was 25mm, the maximum floor heave was 13mm, and the two sides moved closer by 32mm. The on-site monitoring showed that the displacement of the top and bottom plates was 220mm, and the displacement of the two sides was 473mm. The surrounding rock had been effectively controlled.