According to Fresnell's formula, the coefficients of reflection and transmission of every interface of super-wide-angle Sagnac interferometer (SASI) are calculated. The exit solid angle and transmissivity are deduced, and the expression of luminous flux is derived. The luminous flux optical throughput is calculated with the parameters such as sizes and reflective index of glass arms of ZBaF17 and QF14 in a modified super-wide-angle Sagnac interferometer. The solid angle is 1.7316×10-4 rad, the emergent intensity is about 0.4397 of incidence, with AΩ=0.4×10-4 cm2·sr.