The temporally and spatially modulated Fourier transform imaging spectrometer (TSMFTIS) has the merits of high optical throughput, good mechanical stability, and simple interference configuration. However, the number and the density of pixels in the infrared (IR) focal plane array limit the spectral resolution of TSMFTIS. Thus, we proposed the interferometric supersampling levering multiple sub-pixel translations of the focal plane array detector to realize the supersampling of the interference fringes and improve the system’s spectral resolution. The experimental results show that 2.31 cm−1 spectral resolution is achieved by employing a 384×288 uncooled IR detector array.