This paper takes Grice’s Cooperative Principle as an analyzing tool to study the conversations in Catch-22, a representative work of black humor. This thesis proves that the violation of Cooperative Principle can also create black humor. First present a general introduction to Heller and its work at first, which is followed by a brief introduction of cooperative principle. And then case analysis of the conversations creating black humor. This paper takes Grice’s Cooperative Principle as an analyzing tool to study the conversations in Catch-22, a representative work of black humor. This thesis proves that the violation of Cooperative Principle can also create black humor. First present a general introduction to Heller and its work at first, which is followed by a brief introduction of cooperative principle. And then case analysis of the conversations creating black humor.