The invention relates to portable fog droplet particle size detection equipment and method based on image processing. The portable fog droplet particle size detection equipment comprises a light shielding waterproof casing, a miniature digital microscopic image collecting module, a radio frequency data forwarding module, a battery power source management module and a microcontroller module. The method comprise the following steps: by utilizing an image processing technique, collecting fog droplets and an image by the portable fog droplet particle size detection equipment; extracting an effective area of the image, and a micrometer rule marking line by a mobile phone or other computing terminals, wherein a division background comprises a particle area and a gap area; quickly extracting fog droplet particle size distribution by the distortion degree of pixels in an RGB (red, green and blue) color space and a morphological filtering algorithm; calculating actual fog droplet size and distribution rule by a micrometer rule; quickly forwarding and outputting data by a Bluetooth communication module. The portable fog droplet particle size detection equipment and method have the advantages that the environment suitability is strong, the operation difficulty is low, the detection of the equipment is high in speed and accurate, and the characteristics of portability and low equipment cost are achieved.