  As a mysterious celestial body predicted by General Relativity, black holes
have been confirmed by observations in recent years. But there are still many
unknown properties waiting for us to discover, one of the famous problems is
the quantization of black holes. The quantization of black holes gives new
research significance to black holes, but the quantization of black holes is
difficult to prove. Here we propose a new method to verify the quantization of
black holes: Carnot cycle. Our results show that if the black holes have
quantized energy levels, the work W they impose to us via the Carnot cycle
should also be quantized. We indirectly verify the quantization of black holes
by detecting the quantization of W, and contrast it with the classic Carnot
cycle. In addition, we have also verified the correctness of the second law of
thermodynamics under the premise of considering the quantization of black
holes.
