A three-dimensional horizontal axis wind turbine model is tested and numerically studied. The test is carried out in a laboratory wind tunnel. With PIV measurement, the flow fields around the blade in varied rotating speed and wind speed are obtained. Furthermore, the test result is compared with CFD simulation to study the flow fields in more detail, especially the graphs of the velocity vector, under different operating conditions. The relatively good agreement between the test and numerical results is achieved in some conditions. Besides, under some conditions, the test results are different from the numerical ones. To find the reason of the difference, the numerical simulation with transition model is carried out. Results show that with a consideration of laminar flow and transition process, the calculated wind turbine torque is closer to the test value.