The present study aimed ot evaluating the content of the Arabic reading textbook of the first middle grade (boys and girls) in the Kingdom of Saudi Arabia in the light of readability standards. The study attempted to answer the following questions: 1- What are the readability standards, which should exist in the Arabic reading textbook of the first middle grade ( boys and girls ) in the Kingdom of Saudi Arabia? 2- To what extent do these standards exist in the Arabic reading textbook of the fist middle grade (boys and girls ) in the Kingdom of Saudi Arabia? 3- What is the suggested development for the reading textbook of the first middle grade in the Kingdom of Saudi Arabia in the light of the readability standards? To answer the first question: The researcher prepared a list of readability standards ,which was submitted to a jury of specialists. After modifying the list in the light of the jury's views, the lişt was put in the form of a content analysis card for the targeted textbook. The card contained nine main dimensions with 50 readability standards. The reliability coefficient was high (94%). The answer of the second question required the analysis of 50% of the topics of the targeted textbook. The results revealed the existence of: Printing standards with a percentage of ( 100 %) in boys' textbooks), (73.35 %) in girls' textbooks. . Ideas standards with a percentage of ( 96.45%) in boys' textbooks , ( 100%) in girls' textbooks. Word standards with a percentage of ( 87,02%) in boys' textbooks , (86.45%) in girls' textbooks. Grammatical structures standards with a percentage of (80%) in boys' books, ( 48.6%) in girls' textbooks. Rhetorical styles with a percentage of ( 75.7%) in boys' textbooks , ( 73.9%) in girls' textbooks. Sentence standards with a percentage of ( 74.7%) in boys' textbooks, ( 79.25%) in girls' textbooks. Clarity of diction with a percentage of ( 64.35%) in boys' textbooks , ( 70.55%) in girls' textbooks Pictures and graphics with a percentage of ( 50,2%) in boys' textbooks , ( zero ) in girls' textbooks. Adversative sentence with a percentage of ( 41.45%) in boys' textbooks , (58.45%) in girls' textbook. In the light of these results, the study answered the third question, which required a suggested framework for improving the targeted textbook. The study also presented a number of recommendations, the most important of which are defining the readability specifications of school textbooks in general and the reading textbook in specific and not to generalize any textbook in any stage before specifying the degree of readability. o textbooks in ...most important of Shind textbook. The study astion, which required. The study made some suggestions for further research; one of which is conducting a study to improve the content of reading textbooks on the level of the Kingdom of Saudi Arabia and on the level of all stages in the light of readability standards.