At present, there are many studies on the monitor of cutting too1 wear and breakkage and on the monitor of the shape of chips by acoustic emission (AE). In metal cutting process，there are several different AE sources. Moreover，these different AE signals mix with one another. So，the separation of these different AE signals is the key to the monitor of cutting state by AE. In this paper，the separation of the different AE signals in turning process is studied experimentally by making use of a measurement system with wide frequency band and the analysis method of maximum entropy spectrum. The experimental rerults show that the separating different AE signals in frequency domain is feasible.