Subgrade reaction coefficient (SRC) is a key parameter of Winkler foundation model. The benchmark value of SRC is mostly measured by in-situ loading test, and is rarely by indoor testing. In this paper, an apparatus for SRC test is presented and the corresponding testing principles are introduced. The SRC calculation formula is given based on the terminal settlement control method, the equivalent relation of deformation modulus, and the relationship between deformation and time under uniformly distributed load. Moreover, the test steps and calculation method are also introduced. Through comparison between indoor laboratory test and in-situ test, this method has been verified by experiment on fine grained soil valid and reliable. It could be used as a universal indoor testing method for SRC.