A dual-polarization frequency-modulated continuous-wave (FMCW) reflectometer is established on J-TEXT for measuring density profile. The frequency of reflectometer covers both Q band and V band. In order to measure wider density range, ordinary mode polarization and extraordinary mode polarization are utilized at the same time. For the FMCW reflectometer, temporal resolution depends on sweeping rate of the microwave source. Benefited from HTO (hyperabrupt varactortuned oscillator) source, a full frequency sweep period of the reflectometer could be less than 40 μs. Electron density profile from 0-6.0×1019 m-3 can be detected, which covers the whole low field side in J-TEXT. To reconstruct the full density profile, the position of the zero density should be confirmed first, which is determined from where the intermediate frequencies change transiently. Meanwhile, we observe the propagation of left-hand extraordinary wave from data in X-mode reflectometer.