Abstract: Aiming at underwater wall shear stress measurement, researches have been conducted which include MEMS wall shear stress sensors calibration, flat plate model design, weak signal detection system development, flat plate boundary parameter estimation and CFD analysis, and near-wall LDV boundary layer profile measurement. The local free stream velocities ranging from 0.2m/s to 0.7m/s are adopted for the underwater flat plate test in a precision water flume. And the wall shear stress is directly measured by MEMS sensors array. Also the boundary layer profiles of the investigated area upon the plate surface are detected with LDV and mean wall shear stress values are extrapolated. The results from the MEMS sensors match well with those from the LDV velocity profile fittings and are in good agreement with empirical estimations with an overall bias less than 5%.