The knowledge of astronomy in the Middle Ages had two major trends: Astronomy and Astrology. Each one of these two trends has its own characteristics and concepts. Many books on Astronomy and Astrology have been written in Iran. Some of these books, such Suwar Al-Kawākib, Ajayeb Al-Makhluqat, Al-Tafhim, Daghayegh Al-Haghayegh, Al-Bolahan, Al-Mavalid, horoscopes, the Zijs, have been duplicated and illustrated in various periods. Illustration for astronomy, like other scientific fields, has always been the focus of writers and copy vectors to understand difficult topics and help the audience's memory to remember the content. The main question of this research is, what are the characteristics of illustrations of books in the field of astronomy and astrology in Iranian art? The researchers of this article have adopted a descriptive-analytical method and a comparative approach, to present a general view of illustration of astronomy and astrology in Iranian painting, and furthermore to explain the characteristics, differences and similarities, topics and also the methods of implementation of illustration of astronomy knowledge books. The analysis of the related works of art has been done keeping in mind the scientific rules of astronomy. The purpose of the research is to pay attention to the characteristics of illustration in astronomy, astrological books, and also, to compare the type of illustration for the mentioned fields. The results of the research show that the requirement of painters to comply with scientific standards in order to maintain the accuracy of astronomical materials has limited them in the type, style and quality of illustrations in this field, while there were no such strictures for illustrators of astrological books. Illustration of astronomy and astrology books is a combination of realism and fantasy. Astronomy images are often realistic and astrological images are more surrealistic. But the summary of all the differences between astronomy and astrology illustration can be summed up in the fact that the illustrator of astronomy texts is required to follow the rules so as not to damage the scientific accuracy of the text. While there are no such strictures for the illustrator of astrology texts.