We theoretically studied the spin-polarized electron transport properties of quantum waveguide systems with attached stubs in the presence of Rashba spin-orbit coupling （SOC） by the lattice Green function approach. It is shown that the structure-induced Fano resonance and SOC-induced Fano resonance exist in the charge conductance in consequence of the bound states interfering with the conductance states. At the same time, the Fano resonance and antiresonance structures are also found in the spin polarization. In addition, due to the effect of quantum interference and backscattering caused by abrupt change of quantum wire width, a series of resonant peaks and dips appear in the charge conductance and spin conductance. However, all these effects are suppressed and quantization plateau is recovered in the charge conductance and spin conductance when applying a magnetic field to the system. The underlying physics is that the effect of the magnetic field is equivalent to the enhancement of the lateral confining potential, which reduces the intersubband mixing.