Water Vapor Transmission Rate Tester is based on the cup method, and is professionally applicable to the water vapor transmission rate test of plastic films, sheets and laminated materials in medical and construction field. Under a certain test temperature, a constant humidity difference is generated between two sides of the test specimen. The water vapor permeates through the specimen and into the dry side. By measuring the weight changes of the test dish in different time, water vapor transmission rate and other parameters can be obtained.