International aviation organization, governments and most passengers give highly attention to aviation safety. With the advanced science and technology, the aviation technique and application of new skills and materials developed, the aircraft and its operating environment and safety, reliability and economy have been improved day by day. However, in the past 20 years, the slow progress of accidents caused by human factor made the flight accident rate still high. There are plenty of research and analysis on human factor which cause flight accidents at home and abroad, as few on the manuals. This thesis intends to conduct a study in human factor, sums up a large amount of classification and investigation of flight accidents related with manuals, and discusses the impact of manuals on aviation safety. This paper presents corresponding heuristics on the work of preparing manuals and the usefulness of manuals has to be improved further in order to guarantee the aviation safety.