The authors have been developing an autonomous underwater glider which equips an OBEM (Ocean Bottom Electromagnetometer). That is a hopeful instrument for the ocean floor resources explorations. The autonomous vehicle has an ability to achieve a continuous resource exploration autonomously for a long term. The buoyancy and attitude control mechanism of the vehicle enable to move to the next measurement point by gliding. The vehicle which has a blended wing body measures the slight variation of electromagnet wave on the sea bottom and the landing point for the measurement must be precisely controlled by the motion control system. In the landing stage, it is predicted that surface effect of the sea bottom affects the hydrodynamic characteristics of the vehicle, and it might cause some problems on the motion control system of the vehicle. The authors attempt to make clear the characteristics of the flow field around the vehicle in the vicinity of a sea bottom. The motion control system for landing of the vehicle was investigated in the previous study (Yamaguchi and Sumoto, 2019). In this report, hydrodynamic performance of the vehicle in landing is examined by CFD calculations. The surface effect by a sea bottom which affects the lift and drag of the wings of the glider is studied and the characteristics of the blended wing body near a sea bottom is discussed.