Taking the press conference as the dataset of study and the Cooperative Principle as the theoretical basis, this paper examines the phenomenon of the principle of cooperation in diplomatic interpretation and the strategies adopted by interpreters. It is found that from the maxim of quantity, interpreters adopt the method of amplification and omission to meet the necessary and sufficient requirements of information. From the maxim of quality, interpreters carefully choose words to ensure that the information conveyed is accurate. From the maxim of relation, interpreters use paraphrasing to interpret the information in accordance with the specific linguistic environment. From the maxim of manner, interpreters adopt compression strategy to make the target language easy to understand. The Cooperation Principle is of guiding significance to diplomatic interpretation. Interpreters should use it more flexibly to improve the quality of interpretation, so as to achieve effective communication.