Abstract: An improvement to measuring three-dimensional mean flow field in turoo-machinery with a single slanted hot-wire is presented. The method features high accuracy and broad angular measuing range. In order to obtain the three-dimensional flow field, the single slanted wire sets in several positions around the probe axis. The data are sampled with the help of a high speed data acquisition system and the phase-locked ensemble average technique. Then, the three- dimensiorial mean flow field is calculated by means of a data processing program developed by the authors. A periodic three-dimensional flow field at the exit of an axial-flow compressor rotor successfully measured. A proof calculation against the calibration data shows that the errors in velocity measurement are less than one percent of the mean velocity and the errors in the flow direction are less than one degree.