Studying clinical symptoms often meet in the breaking out period of severe level attack of asthma. research was executed in 94 Asthma patients who treated in hospital, the authors realize that there are some factors cause the breaking out such as: after infection, virus infection, environment factors, touching the allergen. Each breaking out often in 5 -20 days. In the night, nearly morning and there are some clinical symptoms often meet to analyze. After researching, the author formulate the prevent methods and treating the breaking out period of asthma better.