The invention discloses an insulator hydrophobic surface local salt density measuring device and a measuring method. The insulator hydrophobic surface local salt density measuring device comprises a water storage tank used for storing deionized water, a water route control module used for controlling deionized water flow rate, a measuring prove used for measuring insulator upper and lower surface local salt density, a circuit control module used for measuring soiling solution resistance value, a selector switch, and a local salt density measuring conversion module used for converting soiling solution resistance value into local coated salt density. The insulator hydrophobic surface local salt density measuring device is of a pincerlike structure; the measuring probe is composed of a pair of parallel electrodes, wherein an external electrode is fixed, and an internal electrode is adjustable, complete contact with composite insulator surfaces and upper and lower surface switching can be realized, direct storing of insulator surface local salt density values can be realized, and measuring stability and accuracy can be improved.