Acoustic emission (AE) monitored tensile tests were performed on 35CrMnSiA steel subjected to different heat treatments. The results showed that quenching and partitioning (Q?P) heat treatments enhanced the combined mechanical properties of high strength and high ductility for commercial 35CrMnSiA steel, as compared with traditional heat treatments such as quenching and tempering (Q?T) and austempering (AT). AE signals with high amplitude and high energy were produced during the tensile deformation of 35CrMnSiA steel with retained austenite (RA) in the microstructure (obtained via Q?P and AT heat treatments) due to an austenite-to-martensite phase transforma-tion. Moreover, additional AE signals would not appear again and the mechanical properties would degenerate to a lower level once RA de-generated by tempering for the Q?P treated steel.