Background: Agriculture is most vibrant field because most of the people having agriculture are main source of living. This field provides food to all living bodies on earth. Need and Methods: Here we discussed a system using machine learning model for the detection and prevention of diseases of plants. For the image processing and analysis, the CNN algorithm is used. It has many advantages for the use in big farms of crops. It automatically detects symptoms of disease whenever they appear on leaves of the plant. In pharmaceutical research, leaf disease detection is necessary and an important topic for research because it has advantages in monitoring crops in the farm and thus it automatically detects signs of disease by image processing by CNN algorithm.