The present book is intended to explain the fundamental principles of synthesis of carbon molecular sieve membranes and also to explore the advantage of employing new modeling technique in optimization of gas separation performance and transport properties. I try that this book provide a complete overview of all the relevant literature but rather to focus on those types of membranes and developments which are forecast to have the most significant impact in future applications. The chapters of this book differ considerably in depth, emphasis and length and, in order to retain the perspectives of the various contributors, no uniformity has been sought in the presentation of the above mentioned subjects. For those chapters where the author has used English as a second language, the editing has been the responsibility of the publisher. I hope that the book will serve as a manual and reference for the industrial and scientist professional academic, while also providing enough basic feed to introduce students to the mentioned subject. It is also our hope that the contents will offer guidance for future development and various industrial applications in this engineering field.