Abstract: A new approach to isothermal precipitation kinetics of carbides in undercooled austenite has been proposed firstly, which is based on measuring the changes of Ms point vs holding time at a certain temperature. The isothermal precipitation kinetics (PTT) Curve of carbides was obtained by the use of the method for 13Cr-8Mn-0.07N stainless steel, and compared with the results of chemical phase analysis and TEM method. The results show that the new method is more sensitive and convenient than the other methods.