Detection and characterization of microwave photon sources is a key step in quantum information. For the optical photons, Hanbury Brown-Twiss interferometer can be used to measure the correlation of them. However, for microwave photons, as the signal-to-noise ratio of them is much lower than that of optical photons,multiple-calculation process is necessary for the elimination of noise influence. Here a new, fast and scalable measurement scheme is demonstrated to characterize a microwave photon source, in which real-time processing and full parallelism are realized by using field programmable gate array (FPGA). And the second-order correlation function of a coherent source with 3 MHz is investigated using the proposed scheme. The good agreement between the output of FPGA and that of the theoretical calculation indicates that, the scheme is promising for application in quantum information processing such as the characterization of microwave single-photon sources.