Abstract: The morphology and distribution of free-cutting phases in free-cutting steel are important factors influencing their cutting properties. In order to develop new austenitic free-cutting stainless steels, the free-cutting phases in chalcogenide（303F, 303Cu, 304F）, lead-based（303Pb）, and selenium-based（304Se） austenitic free-cutting stainless steels were observed and analyzed by metallographic microscopy, scanning electron microscopy（SEM）, energy dispersive spectrometry（EDS）, electron probe microanalyzer（EPMA）, microhardness tester and inclusion three-dimensional corrosion etching technology. The existence forms of each free-cutting element in steel were investigated, and the differences of free-cutting phases and microhardness in each austenitic free-cutting stainless steel were compared. The results showed that among all kinds of austenitic free-cutting stainless steels, the 304（Se addition） steel exhibited the largest average equivalent diameter and average area. Specifically, the average equivalent diameter was 3.66 μm, and the average area was 15.10 μm². The average aspect ratio of inclusions in 304（Se addition） steel was 2.54, and most of the inclusions were ellipsoidal-shaped. The inclusions with aspect ratio of 1-3 accounted for 73%, which was significantly higher than that of 58% in 303Cu steel and 55% in 303Pb steel. The existence forms of free-cutting elements in the steel were different: S in the steel formed free-cutting phase MnS; Cu existed in solid solution in the steel matrix; Pb existed in steel in the form of agglomerate or it was distributed in two ends of MnS; Se formed Mn（Se, S） composite inclusions in the steel which could resist rolling deformation so that the morphology tended to be fusiform; some Mn（Se, S） composite inclusions wrapped the hard Al₂O₃ core to improve the cutting performance of steel. Among various types of austenitic free-cutting stainless steel, 304F steel had the highest average micro-hardness value, which was 309 HV_0.1. The average micro-hardness value of 304（Se addition） steel was 229HV_0.1. Due to the effect of Cu to reduce the strain hardening, the average micro-hardness value of 303Cu steel was the lowest, i.e., 156HV_0.1.