Abstract: The acoustic power of high intensity sound sources reached kilowatts and thes of kilowatts. Many are the sources of modulated air flow. It is somewhat difficult to use the method for measuring usual sound sources to measure high intensity sound sources. As an example, in the method of progressive wave tube, the end of tube must have an exit for air flow, and the absorbers at the end of tube may be under acoustic fatigue easily. When the reflection coefficient at the end reached 0.25, the variation of sound pressure level in tube can-be as much as 2.5 dB,’ and therefore the results have large errors for measuring power. The method presented in this paper permits presence of reflection from the end of tube, and the acoustic power of sound sources is derived from sound pressure level at three location in tube. Analysis proves that the resulting error from the variation of sound field in tube is less then 0.2 dB, when the reflective coefficient at the end is 0.25. The results for 2K sound watts electropneumatic loudspeaker are in agreement for three groups of different measuring points, although reflective coefficient reaches 0.6. In general the error of the results is less then 0.6 dB. The advantages of this method are simpler eguipments and exact results.