Provided is a membrane distillation system capable of real-time monitoring of membrane wetting, which includes: a raw water storage tank configured to store fluid; a membrane distillation water treatment unit configured to receive raw water stored in the raw water storage tank to generate pure water, the membrane distillation water treatment unit having an inlet water chamber into which an inlet water flows from the raw water storage tank, a membrane for separating the inlet water in the inlet water chamber into a steam and a concentrated water, and a treated water chamber for receiving the steam separated by the membrane and concentrating the steam; and a membrane wetting detection unit to detect a membrane wetting phenomenon and a membrane wetting location of the membrane by measuring a light passing through the membrane in real time.