Abstract: The Nan-55 permeameter is widely adopted to determine the coefficient of permeability for fine-grained soils because of its simple structure and easy operation. However, for the permeability tests on undisturbed soil samples, the poor contact between the soil samples and the ring cutter may result in leakage of sidewalls and wrong test results. A new type of Nan-55 permeameter with split ring-cutter structure is developed in order to solve the leakage problem of sidewalls. The side leakage channel between the samples and the ring cutter is blocked by the paste such as Vaseline. What is more, the new-type Nan-55 permeameter has advantages of simple structure and easy operation by adopting the basic structure of the Nan-55 permeameter. At the same time, the reliability of the permeability test results is analyzed, and it is shown that the new-type Nan-55 permeameter effectively overcomes the leakage problem of sidewalls. The coefficient of permeability for the undisturbed fine-grained soils measured by the new-type Nan-55 permeameter has a high accuracy and stability, which are much higher than those measured by the Nan-55 permeameter. The new type Nan-55 permeameter has the prospect to be popularized in the laboratory.