Sir Percy Sykes is one of the most prominent English Orientalist and Iranologist, who had done an extensive research and studies. He, almost, spent half a century in Asian and African countries. In fact, his political and military responsibilities in Iran and his interests in research and studies on Islamic countries led him to travel a lot including six times to Iran. In these travels, he accomplished an extensive and all-dimensional research and collected valuable and useful information. His various works in politics, social, economic, religion, particularly in history and in geography indicate his deep and extensive information.Sykes wrote a book under the title of the History of Iran. In this book, and his other books, besides his direct observation, he used many resources including Greek, Roman, Armenian, Arabic, and the works of French archeologists, British historians and Iranologists. He claims that by writing this book he filled the gap of the past hundred years (from the time of publication of Sir John Malcolm book).This paper will investigate characteristics of historiography of History of Iran. It will review the motivations, goals, perspectives of Sykes, the sources and the way of using them. Also the paper will analyze the effects of the social conditions and the mode of thinking of the time on sir Persi sykes.