Akkermansia muciniphila, as a mucin-degrading bacterium of the phylum Verrucomicrobia, associates with several disease states for its concentration in the human intestinal tract. To accuracy and rapidly measure the concentration of A. muciniphila would be a promising candidate for rapid diagnosis of these diseases. Herein, we present a new method to label-free acquire the concentration of A. muciniphila by designing a graphene-based transistor. Relative permittivities of the transistor were varied by adding A. muciniphila with different concentrations. Various conductance changes, which were recorded by the graphene-based transistor, were generated, and, in turn, characterized the concentrations of A. muciniphila. The experimental results indicated that the approach can significantly distinguish different concentrations of A. muciniphila and has certain fault tolerance when the samples containing a small amount of other intestinal bacteria and impurities. The work offers a general measurement method of the concentration of A. muciniphila, and provide a novel and promising method for the diagnosis of several diseases associating with A. muciniphila.