Abstract: The volume fraction of austenite in high temperature microstructure of duplex stainless steel was measured respectively by the confocal scanning laser microscopy (CSLM) in-situ analysis and solution quenching heat treatment test combined with Mivnt micrograph analysis system in this paper. The results of both methods are generally consistent. Compared to the method of heat treatment, the efficiency and measuring precision of the CSLM in-situ analysis are better. On the basis of the results of the CSLM in-situ analysis and quenching heat treatment test, the linear regress formula between the austenitic volume fraction and temperature is given.