Abstract: Experimental flow data are urgently necessary to study interaction between the sealing flow and main flow in a turbine stage as well as the unsteady flow phenomena of hot ingestion in a disk cavity.However,there are many difficulties in measurements such as light path arrangements due to the narrow space in a rim sealing.Having worked out a lot of technique problems, this paper reports quasi-3D LDV measurements of unsteady flow field in a rim sealing of a turbine stage.The measurements were taken in two steps.First,radial and tangential velocities as well as turbulence intensities were measured using two-dimensional LDV probes put on the casing,then the measurements were repeated by one LDV probe put in the hub.Axial velocity of the flow was calculated from the two sets of data. With the help of a phase-locked technique,the periodically unsteady flow field in both a rim sealing and a disk cavity can be disclosed at different rotor-stator relative positions.This paper presents some typical results of the unsteady flow field.