The characteristics and applicable conditions of a velocity correction method to account for the correction of hydrodynamic forces are investigated by applying computational fluid dynamics (CFD) technique to  oblique towing tests of a KVLCC2 model. The results of numerical method are verified by comparing with the test results in a circulating water channel (CWC). Tamura’s formula on velocity correction is appied to obtain new velocities for tests in wide flow field. Comparisons between hydrodynamics and flow field of the corrected or noncorrected condition and those of CWC test show that Tamura’s formula is applicable to the blockage range of 3.5%－5.0%, while larger blockage leads to drastic changes of flow velocity around the ship. Remarkable difference of the pressure distribution exists along with two sides of the model ship between the tests in CWC and that in wide flow field. The velocity correction increases the pressure of both sides, therefore it reduces the discrepancy within certain blockage ratios and enlarges discrepancy as the ratio continuonsly grows. Meanwhile, correction formula of the lateral hydrodynamic force for low speed fullform ships is proposed based on the blockage correction in a low speed wind tunnel.