Abstract: The hot deformation behavior of as-cast CoNi-based superalloy was investigated by means of hot compression tests. The corresponding microstructure evolution after hot deformation was examined by optical microscope, as well as the TEM technique. The constitutive equation and processing map as a function of deformation temperature and strain rate were developed. Results show that the efficiency peak of the processing map is 0.38 at the temperature of 1130����C and the strain rate of 0.01��s���1. The discontinuous dynamic recrystallization (DDRX) related to the strain-induced grain boundary migration (SIBM) is the dominant recrystallization mechanism during hot working. Meanwhile, the DRX also occurs by forming sub-grains around MC carbides and shear band. In addition, the existence of fine ����� precipitates are found to retard the recrystallization. Graphic Abstract: [Figure not available: see fulltext.].