According to the mission of Helmet Mounted Sight/Display System (HMSDS), an effectiveness evaluation index system was established.Based on ADC model and the characteristics of cloud model to fuzzy problem evaluation, and by calculation of the capacity matrix C, the cloud model algorithm was introduced when calculating the cloud membership value of each index.Thus the cloud membership degree of the system effectiveness was obtained.Finally, analysis was made to the cloud membership degree through simulation, and the influence of cloud droplet distribution on the result of evaluation was given.