A tunable polarization filter is proposed based on one-dimensional photonic crystal with nematic liquid crystal defect. Tunable polarization filtering can be realized dynamically by the electrically controlled birefringence of nematic liquid crystal. The transmission spectra of TM mode are numerically calculated using the transfer matrix method. The results show that the filter has good tunablilty and advantages of simple structure, small volume, easy adjustment, low wastage and narrow pass band. The results imply that this filter has potential applications for wavelength division multiplexing and precision optical measurement.