Based on unpublished documents from the Russian archives and available academic publications, the author presents the first attempt to comprehensively consider the P.N. Perovsky’s activity in China in 1858 - 1859. Perovsky was sent to China with purpose of ratification of the Tientsing treaty concluded by E.V. Putiatin and conclusion of additional agreements for the Aigun treaty, that he has signed himself. Most of purposes of this mission was not achieved. According to the results of research, the author comes to conclusion, that failures of Perovsky, a typical cabinet official, were due both to his lack of experience of diplomatic negotiations, and to the additional resistance of obstinate Chinese dignitaries.