In view of the influence of the fixed floor of low speed wind tunnel on the data quality and test efficiency of ground effect test, the structural parameters of the suction seam and the fairing leading edge of the fixed floor are optimized by CFD calculation method. Based on the non-contact measurement and control method, a fixed floor follow-up sealing device was designed. In the low-speed wind tunnel, the wind tunnel drop coefficient and boundary layer thickness above the optimized fixed floor were measured through the test. The results show that the boundary layer thickness of the optimized fixed floor model can meet the requirements of the ground effect experiment under the common wind speed.