Abstract: A small five hole spherical pressure probe instrumentation system is developed and applied to compressor interstage parameter measurement.This instrumentation system has two features:One is smallness of flow disturbance due to small dimensions of the probe head,the other is an advanced data processing method of this system which comprises perfect probe calibration and data processing procedure.The analysis of the test results demonstrates that its performance is stable,its accuracy and data repeatability of its measurements are quite well.This instrumentation system can be applied to verification of the design parameters.