Abstract: The black hole area theorem shows that the area of the black hole does not decrease，which corresponds to the second law of thermodynamics. We note that the four gravitational wave observations from LIGO come from the merging process of the double black hole，and thus we use these observed data to validate the area theorem. The four observations all support the black hole area theorem. In addition，we study the merge process of N black hole，and a equivalence representation of the area theorem is obtained in principle.

Key words: black hole area theorem, Bekenstein - Hawking entropy, black hole merge, LIGO, gravitational wave