Shearing and imaging principle of the polarization interference imaging spectrometer (PIIS) are presented. Throughput of the PIIS is analyzed and calculated, the changing relation of throughput with deviation is derived under polarizer's polarized direction deviating from the ideal direction. Throughput value in the maximum modulation depth is given. The PIIS has simple structure and no moving parts, high pass through rate of energy. It shows the advantages of ultra-compact, stationary, wide view of field, high throughput and modulation depth. It is more suitable for remote sensing of aviation and aerospace, field operation and weak signal detection.