The acoustic emission (AE) response to brittle cutting of 6H-SiC was studied by molecular dynamics simulation. The micro-deformation and crack formation at atomic scale were analyzed. Furthermore, the AE sources in machining were distinguished and their corresponding AE characteristics were discussed. The results show that the brittle deformation process of 6H-SiC at cutting depth of 77 nm is simple but unusual. The deformation possesses discontinuous dislocation propagation and divides the deformed workpiece into pieces, and then the crack is initiated from a fast dislocation propagation. The compressive stress results in the decline of AE power initially. Three AE sources clustered in the frequency-energy analysis are lattice vibration, dislocation propagation and crack propagation. In addition, the AE response of two times of dislocation propagation shows a higher frequency characteristic than lattice vibration does at temperature of 1 K, with the lowest energy occupation in total. On the contrary, the AE response of crack propagation has apparent frequency and energy accumulation characteristics.