The significance of the existence of the system is to realize its function and maintain its stability, that is, the reliability and stability of the reliability. Reliability is affected by factors, component properties and system structure, and its changes are complex. In order to solve this problem, the authors proposed the space fault tree theory in 2012. This book is the first time that the fundamental part of the theory has been presented internationally. The authors of the book are Pro. Tiejun Cui and Dr. Shasha Li.