<p>Wind turbine main bearing (MB) system concept design requires scoping a lot of optional configurations to find the best one considering both cost and technical feasibility. The paper proposes a high efficient MB system concept design process. In order to efficiently design the wind MB system concept, a MB system configuration modularization and parametric simplification method is developed firstly, then a process to equivalently simplify the complex time series load without losing the dependency of load components is proposed. With the simplified configuration and loads, a MB system technical feasibility assessment method is illustrated in detail, then the MB system weight and cost are roughly estimated. The concept options are characterized by size of MBs and span between bearings, which is convenient for the designer to choose the right concept. The example in the paper shows different MB configuration results in more than 10 % cost difference, while span between bearings only results in less than 3 % cost difference. Bearing configuration should be preferred to span between bearings in concept design.</p>