This paper investigates the generalized Pars ’s theorem of fractional Fourier transform (FRFT) for concentrated data. Also, in the fr a mework of multiple FRFT domains, Pars ’s theorem reduces to an inequality with lower and upper bounds associated with FRFT parameters, named as generalized Pars ’s theorem by us. These results theoretically provide potential valuable applications in filtering, and examples of filtering for LFM signals in FRFT domains are demonstrated to support the derived conclusions