Abstract: 1. The transfer function of .chatter and its extend results. Experiments show that when chatter is excited, the dynamic cutting forces in cross directions are linearly related, i. e. Fc (S) = aFd (S). Here Fc (S) and Fd (S) are individualy the cross force and direct force, a is the linear factor. So the transfer function of the structure is Gd(S)+aGc(S), Gd(S) and Gc(S) are individually direct dynamic compliance and cross one. Therefore, the transfer fuction of the cutting chatter loop should be A system which can be calculated as a single degree of freedom has been designed by the authors for the test. Its damping ratio can be adjusted from 0.03 to 0.8. When chatter is just excited, μ = 0 and the natural damping ratio of the structure just offset by the cutting damping ratio. The results of measuring shows the latter ratio is-0.18. According to the for-mula (3), we can get critical cutting width 21.9mm, and the test value is 20.5mm. But the value of Tlusty formula is 26.97mm.The confirming test has proved the theory and the formulas in this paper are correct. They show that the absolutly stability criterion is not only related to the maxmum dynamic negative part of the real compliance of the structure but also to the maxmum negative coefficient of cutting damping force and the frequency of the chatter. The test show the formula (3) can be used for forecasting the cutting clatter.