Local area velocities have been studied in a tank of φ2m×4.2m with sideentering impellers under the optimal installation location (3 impellers were the average layout; the horizontal angle of deflection β_opt=10°; the vertical angle α=6°; the impeller installation height h=0.75D, and the ratio of the entering length and the impeller diameter L/D=1.44). The results showed that the velocities in the tank are relatively large in the area close to the three impellers. The velocities in a tank with sideentering impellers are different from the flow field in a vertical agitated tank with an axially symmetric, double peak velocity distribution. When just a single impeller was rotating, the peak of velocity on the measurement line of Y*≈1 was moved left to the axis line of the impeller, while when the three impellers were rotating at the same time, the peak of velocity was moved left over the axis line of the impeller to -0.16R. The proportion V*a/V*in a tank with side-entering impellers is larger than the proportion V*a/V* in a tank with a vertical plug impeller, while the proportions of V*t/V* and Vr/V*vary in an opposite manner. It was shown that the velocities became closer to the axial velocities with increasing axial distance; the discharge flow number (Nqd) of three impellers was 0.665, and the estimated value of the discharge flow number (Nqd) of a single impeller was about 91% of that of three impellers. In the vertical plane with an axial distance close to the impeller, the changes in the mean velocity and the axial velocity in the right part of the impeller zone were similar to those in the left part of the impeller zone, but the change of velocities above the half-way line is different from that below (the proportion of discharge flow above the half-way line is 44.2% and the proportion of discharge flow of below is 55.8%). The relationships between the velocity and axialdistance can be fitted as V*=0.402Y*-0.152 for a single impeller and V*=0.454Y*-0.049 for three impellers.