The risk analysis of clinical claims of mechanical ventilator can provide the useful information to the application of the availability and safety of mechanical ventilators. This paper classifies the clinical claims of two types of mechanical ventilations, and tries to find the distribution characteristics of the failure rate of the clinical claims by using the hazard analysis method. All of the distribution characteristics are related to the factors as ventilator design, environment human factors, etc. The method of risk analysis, combining with the classification of clinical claims, is useful for the clinical application and engineering services of mechanical ventilation.