Proceeding towards the magnetic properties, AGNRs are predicted to be semiconductors with non-magnetic ground state, while ZGNRs are low-band gap magnetic semiconductors where the polarized electron spin resides on two opposite edges with anti-ferromagnetic coupling in its ground state. The anti-ferromagnetic coupling between the two magnetic edge states results in poor magnetic moment of ZGNRs in the ground state. The pioneering idea of inducing a half-metallic behavior in ZGNRs by an external electric field opens the possibility of using ZGNRs in spintronics applications. Afterwards, a variety of methods including edge modification, doping have been employed to induce strong ferromagnetic behavior with spinselective control over the ZGNRs properties. One another effective method for achieving a control over electron transport is by exploiting Quantum Interference (QI) effects. This phenomenon has been extensively discussed in molecular junctions consisting of benzene and other π-conjugated systems including radical molecular junctions, where the relative positions of anchoring groups (para or meta) affects the molecular conductance. Recently, QI effects have also been observed in graphene, in different contexts, including junctions, nanoconstrictions and nanoflakes. Valli et al. have demonstrated that the combination of magnetism and QI lead to spin-polarized QI antiresonances in graphene nanoflakes with zigzag edges. Here, in this work our aim is to investigate that how the change in the width of GNR can affect differently spin up and spin down conductance and thus alter the resulting spinfiltering efficiency. Using first principle calculations, we begin with the description of the electronic structure, magnetic and transport properties of pristine AGNRs and ZGNRs in all the possible states, i.e., non-magnetic (NM), anti-ferromagnetic (AFM) and ferromagnetic (FM). Although AFM spin state is ground state of ZGNR, it can be transformed into FM state in the presence of magnetic substrate or under the application of a magnetic field. We demonstrate the plausibility of utilizing GNRs in its ground state as well as low-lying ferromagnetic state to operate as spin filter. The spin-polarized electron transport is investigated by the means of DFT based nonequilibrium Green's function (NEGF) approach wherein the molecular junctions are constructed by reducing the width of scattering region, while keeping the width of electrodes fixed. Our results suggests remarkable width dependent magnetic behavior in ZGNRs with FM configuration arising from the predominance of destructive quantum interference (DQI) effects with the reducing width of ZGNR which eventually controls the spin-polarized electron transmission.