The flow fields in the stirred tank with three different kinds of combined double-impeller agitators: disc turbine + disc turbine (DT-DT, radial impeller), pitched blade turbine + pitched blade turbine (PTD-PTD, axial impeller) and pitched blade turbine + disc turbine (PTD-DT), were investigated in detail by using laser Doppler anemometry. The two-dimensional mean velocity field and the distribution of turbulence intensity were obtained for different impeller spacings. The experimental results show that the impeller spacing has a significant influence on the flow field. To improve flow homogeneity and agitator efficiency, the appropriate impeller spacing should be in the range of 1/2 to 2/3 of the tank diameter.